OS41A-0151
Oceanic And Terrestrial Controls On Chlorophyll -a Abundance Around The Island Of Okinawa, Japan
This research aims to understand key factors affecting ocean surface chlorophyll-a (Chl-a) blooms at a range of scales (both regional and near the coastal zone) around the Island of Okinawa in the western Pacific. The study region is characterised by both the actions of the Kuroshio Current (which brings warm water) and the Asian Monsoon (which provides moist southwest winds in summer and dry northern winds in winter). Due to these influences, Okinawa has a subtropical climate, with a rainy season in the summer months (MJ), and prevailing northerly winds in winter (NDJ). In order to better understand factors which may influence the timing and magnitude of Chl-a blooms in the vicinity of Okinawa, we applied empirical orthogonal function (EOF) analysis to a time series of AVHRR (monthly mean SST from 1985-2006) and SeaWIFS (monthly mean Chl-a from 1998 to 2006) data over two different spatial scales: domain 1 (D1) - a region of the ocean southeast of Kuroshio, and domain 2 (D2) - a sub-region near coastline focused on Okinawa itself. The first EOF mode of SST in regions D1 and D2 (which accounted for more than 90 % in each domain) showed a clear radiation-driven annual cycle: high SST in summer and low SST in winter. The first EOF mode of Chl-a in D1 (which accounted for 51 %) also demonstrated an annual cycle, but in this instance one that mirrored that of SST (i.e. low Chl-a in summer and high Chl-a in winter). The first mode Chl-a EOF in D2 (accounting for 63 % of the total variance) also has a similar annual cycle, displaying a significant correlation (r=0.75, p<0.001) with northerly wind magnitudes, lagged by 2 months, suggesting that the winter monsoon is a major control on the observed Chl-a bloom. However, extreme events such as typhoons can also cause a Chl-a bloom around the coast. As a result of further analysis of daily Chl-a data along the western coastline of Okinawa, it was found that some of the peaks of Chl-a were closely correlated with river discharges associated with heavy rainfall (with a 4~5 days lag), implying that terrestrial runoff may also act as a significant factor affecting Chl-a blooms in D2.
OS41A-0152
Topographically induced seasonal upwelling and ageostrophy of the coastal Tsushima Warm Current
The seasonal variations of the coastal upwelling have been examined along the Japanese shelf area, the pathway of the coastal branches of the Tsushima Warm Current (TWC), the right-bounded current (coast to the right, looking downstream). The seasonal maps of water temperature at 200 m depth shows the rise of the main pycnoclines along the shelf slope due to the seasonal upwelling from May to September based on climatological temperature observations. An eddy-resolving ocean general circulation model is used to investigate the physical processes governing the seasonal upwelling. The TWC flows into the Japan Sea through the shallow Tsushima Straits and goes through the strong curvature of Japanese shelf seasonally forming the seasonal upwelling, a part of the secondary overturning circulation. A sensitivity experiment suggests that the seasonal upwelling is thermally driven by the density gradient between the buoyant TWC and the cold Japan Sea from April to October. Winter cooling plays a significant role as a preconditioning determining the strength of the upwelling. The dynamic balance across the TWC indicates that the subsurface seaward transport or lateral advection term maintains the overturning circulation or upwelling. The horizontal variation in the shelf topography locally critically influences the horizontal pattern of the lateral advection terms, the overturning circulation, and the upwelling.
OS41A-0153
Dynamics and Internal Structure of the Cross-Shelf Circulation During Wind-Driven Coastal Upwelling
A two-dimensional theory of wind-driven coastal upwelling is developed that is comprised of a surface Ekman layer, an interior frictionless layer, and a frictional bottom boundary layer. The theory is built upon the Lentz- Chapman upwelling theory, which has been used to demonstrate the importance of nonlinear cross-shelf momentum flux divergence during upwelling. The new model retains spatially-varying structure in the interior density and velocity fields. The dynamical model for the interior flow is based upon the nonlinear upwelling theory of Pedlosky, which maintains thermal wind balance between the cross-shelf density gradient and the vertical shear in the alongshelf velocity while retaining the cross-shelf advection of density and alongshelf momentum. The structure of the cross-shelf circulation is studied as a function of alongshelf wind stress and Burger number S = α N/f, where α is the topographic slope, N is the buoyancy frequency, and f is the Coriolis parameter. Predictions of the dynamical model are compared with two-dimensional numerical model simulations. During upwelling winds, the dynamical model predicts interior onshore flow high in the water column for large Burger number, and onshore flow in the bottom boundary layer for small Burger number, consistent with the numerical model and with observations.
OS41A-0154
Integrated Monitoring of the Soya Warm Current Using HF Ocean Radars, Satellite Altimeters, Coastal Tide Gauges, and a Bottom-Mounted ADCP
The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. The SWC flows into the Sea of Okhotsk from the Sea of Japan through the Soya/La Perouse Strait, which is located between Hokkaido, Japan, and Sakhalin, Russia. It supplies warm, saline water in the Sea of Japan to the Sea of Okhotsk and largely affects the ocean circulation and water mass formation in the Sea of Okhotsk, and local climate, environment and fishery in the region. However, the SWC has never been continuously monitored due to the difficulties involved in field observations related to, for example, severe weather conditions in the winter, political issues at the border strait, and conflicts with fishing activities in the strait. Detailed features of the SWC and its variations have not yet been clarified. In order to monitor variations in the SWC, three HF ocean radar stations were installed around the strait. The radar covers a range of approximately 70 km from the coast. It is shown that the HF radars clearly capture seasonal and subinertial variations of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in summer, and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The surface transport by the Soya Warm Current shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records. The cross-current sea level difference, which is estimated from the sea level anomalies observed by the Jason-1 altimeter and a coastal tide gauge, also exhibits variation in concert with the surface transport and along-current sea level difference. http://www.lowtem.hokudai.ac.jp
OS41A-0155
Dynamics in Sand of Fecal Indicator Bacteria (FIB) and Salmonella From Contaminated Water, Runoff, and Sewage in an Urbanized Southern California Shoreline
In urbanized coastal watersheds, FIB can come from a variety of sources, including contaminated freshwater sources such as storm drains or creeks, sewage spills, and overlying waterbodies. To investigate the impact of these sources on bacterial levels in coastal sediments and resultant impacts on water bodies, we studied these three source types in Southern California. First, we sampled at 8am and noon at three locations throughout the summer at an enclosed beach on Avalon Bay, Catalina Island, in collaboration with Southern California Coastal Water Research Project. Using membrane filtration and IDEXX substrate technology, we measured FIB levels in sediment and water and observed a positive correlation between these two factors. Second, we studied bacterial persistence in sediment using human sewage as source. To study bacterial survival in the natural environment, we tested solar disinfection with raking as a disinfection procedure after a large sewage spill in the Los Angeles area. First order decay constants for the E. coli ranged between -0.23 and -1.02 in test plots. Further bench scale studies were conducted to determine the effect of various factors on inactivation kinetics. Decay constants measured in controlled experiments in both February and June on the rooftop ranged from -0.73 to -1.54 even though both temperature and intensity of sunlight varied greatly in these months. Interestingly, microcosms subjected to constant moisture had similar decay constants for enterococci, while E. coli in moistened sand showed very low decay rates. Finally, we further investigated effects of sunlight by assessing the extent of surface sand contamination near two contaminated freshwater sources, one under constant shading, and looked for evidence of human fecal matter.
OS41A-0156
Across-shore Eddy Transport off Central California
Kinematic characteristics and physical mechanisms of across-shore transport off Central California were studied using subsurface RAFOS data collected between 1992-2007 and the UCLA ROMS output for meso- and submesoscales. Kinematic characteristics of the transport, including translation speed and direction, period of rotation, and characteristic swirl velocity were estimated from the spectral analysis of RAFOS trajectories directly and from Lagrangian statistics computed using an exit time concept. Pair statistics of floats were also used to understand the physical mechanisms of the westward transport. RAFOS floats demonstrated two types of subsurface westward transport between 300 m and 375 m. First, intensive mesoscale eddies, as well as long-lived submesoscale coherent vortices with diameter of 30-40 km transported floats as far as 1200 km offshore. Data also show that some eddies retained floats for a year or longer. The transport seems to be of an advective type. The kinematic characteristics of the transport were extracted from the float trajectories using spectral and wavelet analysis. Second, other float trajectories were combinations of several irregular loops with rapid translations between them. This motion was interpreted in terms of traps and flights of two-dimensional turbulent motion, and was quantified using the exit time. The relative dispersion of floats followed the ballistic law up to 100 km distance between floats but was exponential when the distance was between 150 and 400 km. To understand the physical mechanisms of the westward transport, the ROMS output with spatial resolution of 3.5 km was used. The results showed that nonlinear interactions between coherent mesoscale eddies play an important role inshore as well as in the Coastal Transit Zone. ROMS demonstrated intensive eddy pairing and merging. Both these processes are a signature of upscale kinetic energy flux. We hypotheze that eddy pairing resulting in coherent eddy dipoles was one of the main factors contributing to RAFOS float dispersion. http://www.oc.nps.navy.mil/npsRAFOS/
OS41A-0157
Wind-drive coastal currents in the Gulf of Tehuatepec: HF radar observations and numerical model simulations.
Most of the studies on coastal dynamics in the Gulf of Tehuatepec (GT) have been focused on mixing processes and mesoscale eddies generated due to strong off-shore wind events, know as Nortes or Tehuanos. In order to investigate the spatial and temporal mesoscale variability of surface dynamic in the GT in February 2005, two HF Radar model WERA were deployed along the shore of Oaxaca, Mexico. The spatial coverage of radars reaches up to 120 km off-shore. The radial velocities were processed to obtain total velocity maps every hour in a regular grid of 5.5 km. space resolution. The information of surface velocity and quickscat/NCEP wind obtained during the first sample days show that exist a coastal current toward the west and, during the wind events, is accelerated and steered toward the southwest. In this same period, we find that spatial density of kinetic energy and divergence of velocity field increase during wind events while the vorticity becomes negative. When strong wind events are not present the surface circulation is weakened, mainly for the zonal component of the wind that is mostly positive (westward). These results are in agreement with the upwelling processes observed on the coast and the anticyclonic eddie generation west of the GT during Tehuanos. Images of sea surface temperature and chlorophyll concentration are also used to observe the signature of wind events near the shore. Complementary to field observations, numerical simulation using a 3D primitive equations model (POM) are used to study the wind-driven circulation in the GT. It has been commonly accepted in previous studies that the strong wind events generate mesoscale eddies. We discuss the limited effect of the wind and the interaction of the wind with a coastal current required to generate long life eddies.
OS41A-0158
The distribution pattern of the red tide and the process of oxygen depletion in the coastal brackish Lake Nakaumi, Southwest Japan
Lake Nakaumi is a coastal brackish water lake formed by the Yumigahama peninsula. The water mass of Lake Nakaumi has two-layer structures. The main halocline divided to Nakaumi Surface Water (NSW) of the intermediate saline water (around 15psu) and Nakaumi Bottom Water (NBW) of the high saline water (about 30psu). Recently, the occurrence of red tide bloom is frequently observed in the lake. The main purpose of this study is to understand the influence of the red tide on the lake environment (The especially, dissolved oxygen in NBW). In this study, we investigated the water quality during April to June 2006 when the lake has experienced extensive occurrence of red tide, and we also monitored the chlorophyll-a (Chl-a) distribution by in vivo fluorometric method. ? Red tide blooms were observed almost in the entire area of Lake Nakaumi in spring, 2006. The water surface showed reddish brown color due to the occurrence of red tide. In the composition of the phytoplankton, Prorocentrum minimum was the dominant species during the red tide. The composition of the phytoplankton rapidly changed during May 27 to 30, and it shifts to the community in which Cyanophyceae is dominant. During that time, the Chl-a concentration rapidly decreased. Based on the vertical distribution of the Chl-a concentration, the red tide at our observation period was divided to 3 phases. In Phase I (March 18th to April 22nd), the Chl-a concentration was relatively low, and homogenous distribution in NSW. In Phase II (April 22nd to May 10th), the Chl-a concentration shows high value, and the peak of Chl-a concentration was present at small-scale and main halocline in the whole water column. In Phase III (May 10th to May 27th), the peak concentrations of Chl-a were distributed around small-scale halocline in NSW and main halocline. In NBW, the Chl-a concentration was low. In Phase I, the dissolved oxygen (DO) concentration of NBW shows 5~7mg/l. During Phase II, DO in NBW decreased. The decreasing in DO tends to remarkably observe at the peak of Chl-a concentration in NBW. Contrastively, the supersaturated condition for DO is observed at the peak of Chl-a concentration in NSW, and it seems to do the active photosynthesis. Because the solar light could not reach to NBW due to high numerous phytoplankton cells, the available DO is consumed by the respiration of Proro. minimum. The sinking of living Proro. minimum may contribute for the decreasing of DO in NBW. It is also considered that DO is consumed to decomposes the dead Proro. minimum, when it sink in NBW. DO in NBW seem to decrease by these synergistic effects. During Phase III, NBW shows the anoxic condition. It is considered that either the living Proro. minimum becomes dormant state or the dead cells as biological aggregates enter into NBW. Therefore, the quantities of phytoplankton do not seem to reflect for Chl-a concentration measured by the in vivo fluorometric method. Because the red tide is disappearing after the formation of anoxic environment at NBW, it may be considered as one of the factors for the disappearance of the red tide.
OS41A-0159
An Integrated Model of Hydrodynamics and Water Quality Transport
his paper presents the development of a numerical model to simulate integrated hydrodynamics and water quality transport in surface waters. The hydrodynamic module solves three-dimensional Navier-Stokes equations with or without the hydrostatic assumptions, and energy and salinity transport equations. The turbulence is modeled with a generalized transport equation. The moving free surface is explicitly handled by solving the kinematic boundary condition equation using a node-repositioning algorithm. The water quality module solves sediment and reactive biogeochemical transport equations. The set of species transport equations were transformed into three subsets using a general paradigm of diagonalization. The first subset constitutes of algebraic equations of equilibrium variables for fast/equilibrium reactions. The second subset is made of transport equations of kinetic variables for slow/kinetic reactions. Finally, the third subset composes transport equations of components for reaction invariance. The Arbitrary Lagrangian-Eulerian (ALE) representation is adopted for all transport equations. To provide robust, accurate, and efficient simulations, a variety of numerical schemes are provided. These include finite element methods or a combination of finite element and Semi-Lagrangian (particle tracking) methods. The model was applied to the Loxahatchee Estuary river system. The computational domain includes the Loxahatchee estuary, Intracoastal Waterways, and three major tributaries of the river - the South Fork, North Fork, and Northwest Fork. The comparison between model simulations and field data is excellent for tides and adequate for salinities. To demonstrate the flexibility and generality of water quality transport module, three widely used water quality models, WASP5, QUAL2E, and CE-QUAL-ICM, were recast in the mode of reaction networks. Simulations of QUAL2E and WASP5 using the model illustrated that they were treated simply as two examples in light of the general paradigm of modeling reactive biogeochemical transport. http://people.cecs.ucf.edu/yeh
OS41A-0160
A statistical model for water quality predictions from a river discharge using coastal observations
Understanding and predicting coastal ocean water quality has benefits for reducing human health risks, protecting the environment, and improving local economies which depend on clean beaches. Continuous observations of coastal physical oceanography increase the understanding of the processes which control the fate and transport of a riverine plume which potentially contains high levels of contaminants from the upstream watershed. A data-driven model of the fate and transport of river plume water from the Tijuana River has been developed using surface current observations provided by a network of HF radar operated as part of a local coastal observatory that has been in place since 2002. The model outputs are compared with water quality sampling of shoreline indicator bacteria, and the skill of an alarm for low water quality is evaluated using the receiver operating characteristic (ROC) curve. In addition, statistical analysis of beach closures in comparison with environmental variables is also discussed. http://sdcoos.ucsd.edu/data/particles/IB/
OS41A-0161
Validating the GSM01 Algorithm for Chlorophyll Products in the Chesapeake Bay
Chlorophyll algorithms are used in ocean remote sensing to process satellite data in order to study the dynamics of primary production. In particular, the GSM01 algorithm distinguishes itself from others through its ability to retrieve chlorophyll and CDOM (colored dissolved organic matter) simultaneously. In order to use this globally- tuned algorithm in the Chesapeake Bay, Andrea Magnuson from the University of Maryland tuned its model parameters regionally and seasonally using in situ data from the bay. Consequently, this research involves the updating of Magnuson's work using two to three more years of in situ data as well as NOMAD, a standardized in situ dataset. In addition, methods for sensitivity analyses on the satellite sensor's wavelength suites, for the selection of inversion used in the algorithm, and for blending regional and global algorithms in chlorophyll images extends the validation. Revision and improvement of this algorithm helps broaden the use of remote sensing products to governmental use as evidence for regulating the health of the bay. On a wider scale, such research contributes to improvements of remote sensing products on the coast.
OS41A-0162
Modeling of Fine Stratified Wake and Internal Waves Structures Past Obstacles
The goal of the talk is to describe a fine flow structure formation in a continuously stratified fluid past uniformly moving obstacles basing on analytical and numerical analysis of set of fundamental governing equations and on visualization of flows by sensitive and high resolution instruments. Mathematical modeling is based on the set of fundamental governing equations including continuity, Navier-Stokes, transport of substances and the state equation with standard no-slip and no-flux boundary conditions for given particular geometry of the problem. At the first step transient diffusion induced flows on a motionless body of perfect shape (plane, cylinder or sphere) are calculated and basic components of the flow are identified. A fine structure of velocity and density fields of the diffusion-induced flow is analyzed. Flows produced by uniformly moving obstacles are calculated in linear approximation taking into account viscosity effects. Analytical calculations reveals set of regular and singular disturbed components describing internal waves, wake and upstream disturbances if a wide ranges of flow parameters. Large number of experiments with different towing bodies in stratified tanks was performed in a wide range of flow parameters. Conditions of well mutual correspondence of analytical, numerical and experimental results are defined. Formation of transverse streaky structures on obstacles and inside the wake and their transformation firstly into sequence of clusters and then into vortex systems is observed. Formation of singular soaring interfaces inside internal wave fields past 2D obstacles ad their gradual transformation into vortices is visualized. Soaring interfaces looks like infinitesimal analogues of shock waves. Due to physics of their formation soaring interfaces are acting as attractors and collectors of contaminants and producing a great impact on redistribution of concentration of diffusive clouds. Data extrapolation on the environmental conditions is discussed.
OS41A-0163
Combining Meteorological Stations and Satellite data to Evaluate the Offshore Wind Power Resource of Southeastern Brazil
Wind is strong and steady over the ocean, but on-site marine meteorological data are sparse. Here we draw on meteorological station, satellite data (QuikSCAT), and both theoretical and practical measures of wind turbine performance. The meteorological stations give high time resolution direct measurements at a few points and provide validation and adjustment of the satellite data. The satellite data provide near-complete area coverage at lower time resolution. For the southern coast of Brazil, we use both data sets to evaluate the location, timing, and availability of the resource. Then, using bathymetry and the properties of current wind-electric technology, we develop maps of wind speed, wind power density, and practical turbine output in power units (GW). In the shallower waters of south Brazil, along only one coastal area situated between 28oS and 33oS we find a total resource of 102 GW average electrical production. The potential electrical output of this one coastal region based on current technology is near today's average electric demand for the country.
OS41A-0164
An Introduction to the Biological and Chemical Oceanography Data Management Office (BCO- DMO)
The BCO-DMO (http://www.bco-dmo.org) was created to serve PIs funded by the NSF Biological and Chemical Oceanography Sections as a facility where marine biogeochemical and ecological data and information developed in the course of scientific research can easily be disseminated, protected, and stored on short and intermediate time-frames. The Data Management Office also strives to provide research scientists and others with the tools and systems necessary to work with marine biogeochemical and ecological data from heterogeneous sources with increased efficacy. To accomplish this, two data management offices (former- U.S. JGOFS and U.S. GLOBEC) have been united and enhanced to provide a venue for contribution of electronic data/metadata and other information for open distribution via the World Wide Web. The JGOFS/GLOBEC Client/Server distributed data management system software is used to serve data and information to every investigator, regardless of computing platform. In addition, Web services are provided for data discovery, and development has begun on a machine-to-machine application programming interface (API) to allow interoperability between Web-based data systems. The BCO-DMO will manage existing and new data sets from individual scientific investigators, collaborative groups of investigators, and data management offices of larger multi-institutional projects via any standard Web browser. The office will work with principal investigators on data quality control; maintain an inventory and program thesaurus of strictly defined field names; generate metadata (e.g. Directory Interchange Format (DIF) ) records required by Federal agencies; ensure submission of data to national data centers; support and encourage data synthesis by providing new, online, Web-based display tools; facilitate interoperability among different data portals; and facilitate regional, national, and international data and information exchange. http://www.bco-dmo.org
OS41A-0165
Past Occurrences of Hypoxia in the Baltic Sea
The hypoxic zone in the Baltic Sea has increased in area by about four times since 1950. Widespread oxygen deficiency below the halocline has severely reduced macro benthic communities in the Baltic Proper and the Gulf of Finland over the past decades and negatively effected food chain dynamics, fish habitats and fisheries in the entire Baltic Sea. In addition, hypoxia alters nutrient biogeochemical cycles. The cause of the increased hypoxia is believed to be enhanced eutrophication through increased anthropogenic input of nutrients, such as phosphorous and nitrogen. Conditions prior to the 1950s are considered as the benchmark and some authors suggest that the earlier Baltic Sea was an oligothrophic, clear-water body with oxygenated deep waters. By contrast, studies of short sediment cores reveal that hypoxia has been present in some of the deepest basins for at least the last 100-200 years. In addition, long sediment cores suggest that hypoxia in the Baltic Sea has occurred intermittently in deep basins over the last c. 8500 years. Thus, the occurrence of present day hypoxia in the deeper basins need not necessarily be attributed to human activity but rather to natural oceanographic, geologic and climate conditions. We present a compilation of previous publications that reported the occurrence of laminated sediments (i.e. a palaeo-proxy for hypoxia) in the Baltic Sea. This review shows that the deeper parts of the Baltic Sea have experienced either intermittent or more regular hypoxia during most of the Holocene and that more continuous laminations started to form c. 7800-8500 cal. yr BP ago, in association with the establishment of a permanent halocline during the transition from the Ancylus Lake to the Littorina Sea. Laminated sediments were more common during the early and late Holocene and coincided with intervals of high organic productivity (high TOC content) and high salinity during the Holocene Thermal Maximum and the Medieval Climate Optimum. This study implies that there may be a correlation between past climate variability and the state of the marine environment, where milder periods correspond to increased primary production and higher salinities resulting in amplified hypoxia and enlarged distribution of benthic mortality and laminated sediments.
OS41A-0166
On Thermally Forced Upwelling in a Small bay With Application to Concepción Bay, Chile
An analytical model describing thermally forced upwelling in a semi-enclosed deep bay is presented. The model is 2-dimensional (integrated in the lateral direction) and models the vertical circulation as response to a surface heat flux. It is assumed that the water outside the bay is kept cold. The cold water enters the bay where it becomes exposed to intense heating and thus becomes less dense. The heated and low-density water forms an outward directed divergent surface current which gives rise to an upwelling spread over the bay and a compensating inflow of cold water at depth. It is assumed that the scales are such that the surface layer outflow is geostrophic. The model is thought to be applicable to a bay at a low-latitude coast where large-scale upwelling along the coast brings cold water to the surface (e.g. Chile). Four equations are used: conservation of heat in the surface layer, geostrophic surface outflow, continuity of volume and a mechanical-energy equation. The model is forced by a constant surface heat flux. The system of equations is solved using dimensional analysis, and thus leaves a universal non-dimensional constant to be determined by observations. The model predicts a divergent outflow in the heated surface layer, which increases linearly (for a rectangular bay) from the head of the bay. The upwelling velocity is thus constant and so is the surface excess temperature. Numerical experiments using a 3D-model in a simple setup show similar response after a few days of spin up. The model predictions are found to be in reasonable good agreement, both in a qualitative and a quantitative sense, with observations from Bahia de Concepción, Chile, during some summer days with low winds. The intense upwelling in the bay those days resulted in a very high primary production as was indicated by the green colour of the water and the small Secchi-disk depth).
OS41A-0167
High Resolution Bathymetric LIDAR Measurements at San Luis Obispo Bay, CA
The movement of sand by ocean currents is an invisible but critically important phenomenon to coastal communities and sea-vessel-dependent economies such as in San Luis Obispo Bay. Over time, sand (or sediment) can cause beaches to erode or rebuild and harbors to "silt up." Dredging harbors is an obvious control mechanism, but the process is messy and expensive. Thus, such "coastal management" decisions should be well informed. Unfortunately, the effect of ocean currents on sand and sediment levels on the ocean floor is poorly understood in part because it is hard to observe: it occurs at the bottom of the ocean. But questions remain: What are the sand movement dynamics at the bottom of San Luis Obispo Bay? Is the bay filling in? Emptying out? What effects do persistent wind and wave patterns have on the ocean bottom? What about large storms? In order to answer these questions, we have installed a bathymetric Light Detection And Ranging (LIDAR) system on the Cal Poly Center for Costal Marine Sciences Pier in Port San Luis Obispo, California. Using a 1 Watt Nd:YAG laser operating at 532nm and a single photon detector, we have observed photons scattered off the ocean floor (benthic boundary layer or BBL). The photon detector is attached to a high resolution, multiple-stop timer, with 15 picoseconds of event-to-event resolution. This yields an approximate 1 cm resolution of LIDAR ranging and hence sediment transport dynamics. In this poster, we will present preliminary results of our work including evidence of surface- and BBL-scattered photons. http://atom.physics.calpoly.edu/faculty/index.php/LIDAR
OS41A-0168
Creation Of Constructed Tidal Flats Using Ocean Dredged Sediment
The enforcement of London dumping convention (1972) and protocols (1996) which are comprehensive assessment system for ocean dumping wastes needs environmentally sound treatment and/or reuse of dredged sediment. Creation of constructed tidal flats using dredged sediments could be one of the useful alternatives among other dredged sediment treatments. In this study, the pilot-scale constructed tidal flats with 4 different mixing ratio of ocean dredged sediment were constructed in Nakdong river estuary, Korea. The reed was transplanted from the adjacent reed community after construction, and then the survival and growth rate of the planted reed was measured. Also the changes of Chemical Oxygen Demand (COD), Ignition loss (IL), and the heterotrophic microbial numbers were monitored. The survival rate of the planted reed decreased as the mixing ratio of dredged sediment increased. The survival rate of reed in the constructed tidal flat with 100% dredged sediment was 54% while that in the tidal flat with 0% dredged sediment (original soil of Nakdong river estuary) was 90%. There was little difference of length and diameter of the reed shoot among the 4 different constructed tidal flats. 30% of COD and 9% of IL in the tidal flat with 100% dredged sediment decreased after 202 day, however, the consistent tendency in the change of COD and IL in the other tidal flats was not found possibly due to the open system. It was suggested that the construction of tidal flats using ocean dredged sediment can be possible considering the growth rate of transplanted reeds and the contaminated ocean dredged sediment might be biologically remediated considering the results of decrease of organic matter and increased heterotrophic microbial number in the tidal flat with 100% dredged sediment. However, the continuous monitoring on the vegetation and various environmental factors in the constructed tidal flats should be necessary to evaluate the success of creation of constructed flats using dredged sediments and the possibility of natural attenuation of the contaminated dredged sediment in the constructed tidal flat system.
OS41A-0169
Strong Coastal Current Caused By Superposition Of Coastal-Trapped Waves And Near- Inertial Internal Waves Along The Northwest Coast Of Japan
Mooring observations using electro magnetic current meters were performed at 15 m depths around the Tango Peninsula located at the northwest coast of Japan from June 5 to June 27 2004 to clarify the mechanism generating a strong coastal current induced around the peninsula. Typhoon 0406 had passed through over the Tango Peninsula during the observation period. Strong current flowing along the coast on the right was observed one half-day after the typhoonfs passage, and its maximum current velocity was 53 cm s-1. The current field moved along the coast on the right with traveling speed of about 0.6 m s-1 and decreased its strength with propagating. The phenomenon was considered to be induced by superposition of the subinertial fluctuation and near-inertial fluctuation caused by the typhoon. The near-inertial energy was large in the eastern side of the peninsula. The generation mechanism of the strong current was investigated by numerical experiment using multilayer level model with realistic topography and wind stress. The model well reproduced the characteristics of the strong alongshore current. Energy flux density of the subinertial fluctuation flowed along the coast on the right, and the phenomenon was considered to be a coastal-trapped wave (CTW) induced by alongshore wind stress. The near-inertial fluctuations were found to have baroclinicity and construct complex oscillation system around the peninsula. A part of the energy flux density of the near-inertial fluctuation originated from the eastern offshore region of the peninsula was trapped by the eastern coast of the peninsula. In the offshore region, the near-inertial fluctuations were considered to be near-inertial internal gravity waves induced by the typhoon. To clarify the energy concentration process of near-inertial fluctuation to the eastern coast of the peninsula, propagation characteristics of near-inertial internal waves around simplified peninsula were then investigated by additional numerical experiment. It was found that scattering of the near-inertial internal waves occurred around tip of the simplified peninsula, and a part of the energy was trapped and propagated along the coast as internal Kelvin wave.
OS41A-0170
Fine Scale Structures in Space-Time Variability of Light and Temperature in Nearshore Coastal Waters
We describe a method of measurement, analysis, and characterization of light and temperature variation at multiple spatial and temporal scales in the upper three meters of the nearshore water column. These waters exhibit complex thermal and optical properties due to variation in incident solar radiation, primary productivity, sediment transport, as well as variation in the periodicity and magnitude of wave and tidal dynamics. Our conceptual framework for the exploration of structure in the light and temperature space-time dynamics of this complex environment relies on the differences in the measurements of paired observations at fixed spatial and temporal lags. Three full spectrum light and temperature sensors were deployed vertically at six horizontal positions along a 30 meter anchored linear array in the inland fjords of Clayoquot Sound British Columbia for multiple days during the summers of 2006 and 2007. These sensors recorded a time series at 3 minute intervals providing direct paired observations at 15 spatial and 2000 temporal lags. Using Python scripts to define modular functions for computing and displaying the mean difference of each individual pair observation at each spatial and temporal lag, we construct a series of space time surface plots which illustrate iso-lines of similarity in the variation of spatial and temporal structure. The non-stationarity of these surfaces illustrates space-time processes in this environment operating within the 15 meter spatial and 100 to 120 minute temporal scales. We provide architecture for and an explanation of the analysis method as well as the graphic output used in this research.
OS41A-0171
Tidal Exchange Variation On Pier Bridge Between Busan New-port And Nakdong Estuary, Korea
This study analyzes the characteristics of tidal exchange between Nakdong estuary and Busan New-port. Therefore Compact-EM current meter was established on a connecting pier bridge and current velocity was analyzed for flow direction. Observation of tide and C.T.D(Conductivity Temperature Depth) was also analyzed to determine the characteristics of sea water and described the tidal exchange between Nakdong estuary and Busan New-port. For the purpose of indicating characteristics of tidal exchange numerical modelling was used. From the results of measuring the component of current velocity on the connecting pier bridge, it was determined that the dominant outflow direction in ebb tidal current was from the Nakdong estuary to Busan New-port. However, in flood tidal current the dominant direction was from the Busan New-port to the Nakdong estuary. Sum of volume transport of sea water calculations revealed (+)8.076 × 10{6} m{3} on the connecting pier bridge. It showed the volume transport of sea water to be more from Busan New-port to Nakdong estuary than in going the other direction.
OS41A-0172
A Study On The Characteristics Of Deposition In Nakdong Estuary, Korea
Nakdong estuary is located at south-eastern coast of the Korea. A lot of sediment from the upper river is deposited in this area. It has caused many problems such as changes in tidal currents and topography. In this paper, field observation data on tidal currents and sediments were investigated as well as historical topographic changes by dredging and reclamation of the foreshore. Then, the numerical model considering settling velocity was applied to examine the characteristic of deposition. Changes of characteristic of deposition were caused by topographic changes of Nakdong estuary and characteristics of deposition were influenced by river plume and tidal currents.
OS41A-0173
On the instability leading to rip currents due to wave-current interaction
We re-examine the hydrodynamic instability due to wave-current interaction and leading to the formation of rip currents (i.e. nearshore circulations) on beaches which are alongshore uniform. Attention is restricted to normally incident waves and the region inside, and just offshore of, the surf zone where linearized shallow water waves are applied. The coupling of waves and circulations is modelled using the concept of wave radiation stresses and the classical ray theory. It is shown that when the fully dynamical interactions of waves and currents are duly accounted for, and proper mathematical analysis is carried out, the instability not only exists, but also leads to rip currents with scales comparable to field observations. The instability properties, in terms of the neutral modes, the most unstable mode and the corresponding maximum growth rate, are examined in the domain of parameters which represent the effects of offshore wave height and bottom friction dissipation. Comparisons with observations of natural rip currents are made, and qualitative agreements are achieved.
OS41A-0174
Currents and Stratification on the Continental shelf to the Southwest of San Clemente Island, CA
Results of moored current, pressure, temperature and salinity measurements from January 2006 to July 2007 at 130 m depth on the continental shelf offshore Eel Point, San Clemente Island, CA, (mooring located at 32° 55.73'N, 118° 35.50'W) are presented. Statistics for the flow and stratification are presented including probability distribution functions, empirical orthogonal functions, and spectra. The flow field was dominated by persistent poleward flow with two-three flow reversal events per six month period. The structure and possible causes of these flow reversal events are described. Tidal analyses are also presented; higher harmonics of the M2 tide were statistically significant for the onshore flow component.
OS41A-0175
Hydrographic monitoring of moderate El Nino 2006 off the Southwestern Coast of Mexico
Hydrographic data from monthly surveys off the Southwestern Coast of Mexico (near Barra de Navidad) and time series of temperature, salinity and sea level from a mooring deployed 1 km off the coast, for the period 2005-07, are analyzed. Temperature and salinity profiles for the 2006 summer-fall seasons differ from similar profiles obtained in 2005. The differences might be due to the input of large volumes of relatively warm and less saline water, with TS (temperature-salinity) characteristics suggesting a Tropical Pacific origin. By October 2006, those water masses had filled the whole 50m upper layer. Time series of temperature, salinity and sea level at the mooring location for a time period longer than a year, since June, 2006, have shown the passage of coastal trapped waves through the polygon. These waves caused fluctuations of temperature, salinity and sea level up to 10 degrees centigrade, 0.6 psu and 20 cm, respectively.
OS41A-0176
Gulf of the Farallones tidal variation
Three high frequency radar instruments (CODAR) began monitoring sea surface currents in the Gulf of the Farallones off the Coast of San Francisco, California in May 2006 as part of the State Coastal Conservancy funded Coastal Ocean Currents Monitoring Program (COCMP). This has provided an unprecedented spatial and temporal view of sea surface currents in this region. Previous studies have examined the complex surface currents in the Gulf of the Farallones using moored acoustic Doppler current profilers (ADCPs) and ship-mounted ADCPs but these studies did not have as long a time frame nor the spatial and temporal resolution that is now available with HF radar. One of the aims of this project is to develop and test a process in which harmonic tidal analyses are performed to separate out calculated tidal currents from HF radar measured currents. A second goal of this project is to measure cross-shore characteristics of tidal currents. These characteristics include variations in tidal forcing, subtidal forcing, and wind forcing, along with the orientation and rotation of tidal ellipses.