Nencioli F.,University of California at Santa Barbara |
Chang G.,Sea Engineering Inc. |
Twardowski M.,WET Labs Inc. |
Dickey T.D.,University of California at Santa Barbara
Biogeosciences | Year: 2010
Optical properties were collected along a transect across cyclonic eddy Opal in the lee of Hawaii during the E-Flux III field experiment (10-27 March 2005). The eddy was characterized by an intense doming of isopycnal surfaces, and by an enhanced Deep Chlorophyll Maximum Layer (DCML) within its core. The phytoplankton bloom was diatom dominated, evidencing an eddy-induced shift in ecological community. Four distinct regions were identified throughout the water column at Opal's core: a surface mixed layer dominated by small phytoplankton; a layer dominated by "senescent" diatoms between the bottom of the upper mixed layer and the DCML; the DCML; and a deep layer characterized by decreasing phytoplankton activity. We focused on two parameters, the ratio of chlorophyll concentration to particulate beam attenuation coefficient, [chl]/ c, and the backscattering ratio (the particle backscattering to particle scattering ratio), b̃bp, and tested their sensitivity to the changes in particle composition observed through the water column at the eddy center. Our results show that [chl]/ c is not a good indicator. Despite the shift in ecological community, the ratio remains controlled primarily by the variation in chlorophyll concentration per cell with depth (photoadaptation), so that its values increase throughout the DCML. Steeper increase of [chl]/ c below the DCML suggest that remineralization might be another important controlling factor. On the other hand, b̃bp clearly indicates a shift from a small phytoplankton to a diatom dominated community. Below an upper layer characterized by constant values, the b̃bp showed a rapid decrease to a broad minimum within the DCML. The higher values below the DCML are consistent with enhanced remineralization below the eddy-induced bloom. Both the "senescent" and the "healthy" diatom layers are characterized by similar optical properties, indicating some possible limitations in using optical measurements to fully characterize the composition of suspended material in the water column. The inverse relationship between b̃bp and [chl]/ c, reported by others for Case II waters, is observed neither for the background conditions, nor in the presence of the eddy-induced diatom bloom. Between the two parameters, only the backscattering ratio showed the potential to be a successful indicator for changes in particle composition in Case I waters. © Author(s) 2010.
Chang G.,Sea Engineering Inc. |
Twardowski M.S.,WET Labs Inc.
Journal of Geophysical Research: Oceans | Year: 2011
We computed the modulation transfer function (MTF), which is the magnitude of the Fourier transform of the point spread function, for two different water bodies using measurements of optical properties and analytical formulations. Knowledge of the MTF is important for the interpretation of images from underwater electro-optical systems. The data were collected from two field sites as part of the Office of Naval Research sponsored Radiance in a Dynamic Ocean program: (1) Scripps Institution of Oceanography (SIO) Pier, a shallow-water, eutrophic environment, and (2) the Santa Barbara Channel (SBC), a deeper, mesotrophic environment. Wavelet analysis was employed to investigate the sources of variability of the MTF and the periodicities at which they occur. Results suggest that the MTF was strongly related to wind conditions and advection events and the optical properties serving as proxies for particle concentration and composition in the SBC. Increased wind speeds and stresses resulted in upper water column mixing, decreased water clarity, and reductions in image transmission. Rip currents accompanied by high concentrations of reflective particles observed at SIO Pier resulted in increases in the MTF. Optically derived particle composition characteristics such as the bulk particle real index of refraction and particle size distribution are shown to be related to the variability of imaging performance at both field sites. © 2011 by the American Geophysical Union.
Chang G.,Sea Engineering Inc. |
Jones C.,Sea Engineering Inc. |
Twardowski M.,WET Labs Inc.
Methods in Oceanography | Year: 2013
Forecasting Optics REaltime in Shallow Energetic Environments (FORESEE) was developed for predictions of underwater visibility in dynamic surf zone environments. FORESEE employs key measurements of physical forcing and beam attenuation coefficient (beam c) and numerical wave and hydrodynamic models to: (1)generate predictions of energy variation, (2) relate energy characteristics to the optical property of interest, beam c, and (3) produce 24-hr forecast maps of spatially resolved visibility conditions at a site of interest. FORESEE beam c prediction performance was very good using site-specific data collected in Waimanalo, Hawaii (average root mean squared error of 0.38m-1). Predictions of probability of object detection (Pd) were on average within 75% accuracy for 2-m diver visibility. Differences between modeled and measured Pd may have been affected by a phytoplankton bloom that was observed during field data collection. The addition of a growth term and a bottom-type term to the model could account for biological processes and differing bottom types in nearshore regions. Further improvements could also be made with more accurate model boundary conditions. © 2013 Elsevier B.V.
Jones C.A.,Sea Engineering Inc |
Jaffe B.E.,U.S. Geological Survey
Marine Geology | Year: 2013
Morphological trends of three distinct intertidal environments in South San Francisco Bay were investigated using a combination of measurement and modeling tools. Because of the inherent relationship between the physical environment and the sediment properties, the sediment properties provide a good indicator of morphologic trends. A significant finding of this study is that surface sediment erodibility increases as the energy level in the environment increases. Conversely subsurface sediment erodibility shows a strong relationship to the long-term history of the site. The combination of the measured sediment properties, the history of deposition and erosion, and simple modeling of the physical environment illustrate the interaction of these properties such that an understanding of intertidal flat behavior is developed. © 2013 Elsevier B.V.
Goody C.,Sea Engineering Inc.
OCEANS 2013 MTS/IEEE - San Diego: An Ocean in Common | Year: 2013
Sea Engineering, Inc. conducted a detailed 14-month study to investigate sand transport processes and beach erosion at Kapa'a Beach and develop beach improvement alternatives. The study consisted of the following key components: evaluation of sand transport mechanisms and processes acting along the shoreline at Kapa'a; identification of potential beach material borrow sites and available volumes through a geophysical investigation of offshore sand deposits; development of computational wave and circulation models for nearshore Kapa'a Beach using advanced numerical modeling and visualization software; and, development of coastal engineering improvement concepts for mitigation of beach loss and shoreline retreat at Kapa'a Beach. © 2013 MTS.
James S.C.,Sandia National Laboratories |
Jones C.A.,Sea Engineering Inc. |
Grace M.D.,Sandia National Laboratories |
Roberts J.D.,Sandia National Laboratories
Journal of Hydraulic Research | Year: 2010
A detailed description of how recently-developed sediment dynamics formulations are incorporated into the United States Environmental Protection Agency's Environmental Fluid Dynamics Code is presented. The new approach is an extension of previous models and accounts for multiple sediment size classes, has a unified treatment of suspended load and bedload, and appropriately replicates bed armouring. The resulting flow, transport, and sediment dynamics model is an improvement to previous models because it may directly incorporate site-specific data, while maintaining a physically consistent, unified treatment of bedload and suspended load. Experimental data from a noncohesive sediment erosion experiment in a straight channel help validate the numerical model. In this simulation, unknown parameters representing the active layer thickness and the erosion rates of the two largest sediment size classes when they are newly deposited are identified from the available data. © 2010 International Association for Hydro-Environment Engineering and Research.
Barry J.H.,Sea Engineering Inc.
OCEANS'11 - MTS/IEEE Kona, Program Book | Year: 2011
Sea Engineering, Inc. (SEI) has continued long-standing efforts to find exploitable offshore sand resources for the purpose of nourishing Hawaii's beaches. Investigations by University of Hawaii researchers in the 1970's established the potential presence of large bodies of sand in ancient offshore alluvial channels and wave-cut terraces. Sampling efforts showed that much of the sand was too fine-grained to be useful as beach nourishment. Prospecting was revived in the early 1990's with funding for new surveys provided by the U.S. Bureau of Mines through the Marine Minerals Technology Center at the University of Hawaii. The realization that existing instrumentation was not adequate for useful imaging of Hawaii sand deposits led to a team effort by SEI and Precision Signal, Inc., funded by CEROS to develop a state-of-the-art sub-bottom profiling system. The new chirp profiler resulted in excellent sub-bottom imagery. SEI successfully mapped selected sand deposits with the new instrument around the island of Oahu for the United States Geological Survey (USGS) in 1996 and 1998. © 2011 MTS.
Goody C.,Sea Engineering Inc. |
Ericksen M.,Sea Engineering Inc.
Sea Technology | Year: 2012
An important factor in determining dredge-related turbidity impacts is the amount and nature of suspended sediments introduced into the water column and how those suspended sediments are transported and deposited on the seafloor. Existing data documenting how sediment is released into the water column is limited, and the data that are available are primarily derived from US mainland harbor dredging projects, which are significantly different environmentally than tropical reef environments such as those in Guam. The technique requires careful correlation of the measured acoustic backscatter intensities with corresponding water samples, which must be analyzed to determine TSS concentration along with other water column properties such as temperature and salinity. Sediview, from DRL Software Ltd. (Wallingford, England), was used to post-process the ADCP data and perform backscatter-to-TSS correlation. The program computes sediment concentrations from relative backscatter intensity correcting for offsets due to environmental conditions, operating conditions and from the instrument itself.
Sullivan S.P.,Sea Engineering Inc.
Coastal Engineering Practice - Proceedings of the 2011 Conference on Coastal Engineering Practice | Year: 2011
Kaumalapau Harbor is a small barge harbor located on the southwest coast of the island of Lanai in the State of Hawaii, U.S.A. The harbor was protected by an old, deteriorated, rock rubblemound breakwater, originally constructed in 1925. The breakwater was recently completely rebuilt by the U.S. Army Corps of Engineers, Honolulu District, in association with the State of Hawaii. Oceanographic design considerations included a water depth of about 21 m (70 ft) and direct exposure to possible 10.7 m (35 ft) hurricane strength storm waves. The repairs utilized an armor layer of 31.8 tonne (35 ton) Core-Loc™ concrete armor units, the largest units of this type used to-date. The use of Core-Loc units, a relatively new armor unit type, presented both design and construction challenges to insure that their performance capability was maximized. Particular attention was placed on developing a Core-Loc placement plan to achieve the required unit packing density, and utilizing rigorous construction techniques to achieve the specified armor layer placement. This project contributed significantly toward furthering design and construction guidelines for Core-Loc use. Construction was completed in 2007, and the project won the ASCE, Hawaii Section, 2008 Outstanding Civil Engineering Achievement Award. © 2011 ASCE.
Sea Engineering Inc. | Date: 2014-07-22
Embodiments are directed towards a wave measuring electronics device that is integrated within a buoy and the buoy is moored in an ocean. The wave measurement device performs a computer-implemented method for estimating wave motion, including receiving 3D sensor data from each of an accelerometer and a gyroscope, determining, an absolute orientation of the buoy based on said 3D sensor data; and estimating, the true earth acceleration of the buoy over a specified time interval.