OS52A-01
An Information Infrastructure for Coastal Models and Data
Advances in semantics and visualization have given rise to new capabilities for the location, manipulation, integration, management and display of data and information in and across domains. An example of these capabilities is illustrated by a coastal restoration project that utilizes satellite, in-situ data and hydrodynamic model output to address seagrass habitat restoration in the Northern Gulf of Mexico. In this project a standard stressor conceptual model was implemented as an ontology in addition to the typical CMAP diagram. The ontology captures the elements of the seagrass conceptual model as well as the relationships between them. Noesis, developed by the University of Alabama in Huntsville, is an application that provides a simple but powerful way to search and organize data and information represented by ontologies. Noesis uses domain ontologies to help scope search queries to ensure that search results are both accurate and complete. Semantics are captured by refining the query terms to cover synonyms, specializations, generalizations and related concepts. As a resource aggregator Noesis categorizes search results returned from multiple, concurrent search engines such as Google, Yahoo, and Ask.com. Search results are further directed by accessing domain specific catalogs that include outputs from hydrodynamic and other models. Embedded within the search results are links that invoke applications such as web map displays, animation tools and virtual globe applications such as Google Earth. In the seagrass prioritization project Noesis is used to locate information that is vital to understanding the impact of stressors on the habitat. This presentation will show how the intelligent search capabilities of Noesis are coupled with visualization tools and model output to investigate the restoration of seagrass habitat.
OS52A-02
Assimilation of High-Frequency Radar Currents in a Nested Model of the West Florida Shelf
High-Frequency Radar Currents are assimilated in a West Florida Shelf (WFS) model based on the Regional Ocean Model System (ROMS) which is nested in the Atlantic Hybrid Coordinate Ocean Model (HYCOM) to include both local and deep-ocean forcing, particularly the Gulf of Mexico Loop Current (LC). An ensemble simulation of the WFS ROMS model is carried out under different wind forcings in order to estimate the error covariance of the model state vector and the covariance between ocean currents and winds. Radial currents measured by HF-Radar antennas near St. Petersburg and Venice, FL, are assimilated using this ensemble-based error covariance. Different assimilation techniques using a time-average ensemble, a filter to reduce surface-gravity waves and an extended state vector including wind stress were tested. Results of WFS ROMS model assimilating surface currents show an improvement of the model currents not only at the surface but also at depth.
OS52A-03
On the residual circulation in Tampa Bay
Residual circulation in estuaries usually display a characteristic estuarine circulation pattern with inflowing deep waters and outflowing surface waters. The strength being dependend on the tidal prism and the fresh water inflow to the estuary. In estuaries with a strong circulation this leads to formation of distinct water masses. However, in estuaries where vertical mixing is significant, at least part of the time, the importance of the residual circulation for transport of dissolved substances may be seriously reduced. The talk will draw upon recent work using the MIKE 3 unstructured mesh circulation models, set up as part of the USGS Tampa Integrated Science Project. The significance of the residual transport, the quantification of it in a typical Gulf Coast estuary and the relevance for estuarine management strategies will be discussed. http://www.dhigroup.com/Software/Marine/MIKE3.aspx
OS52A-04
Assimilation of Current Measurements Into a Circulation Model of Lake Michigan
We present a method for assimilating current observations into a two-dimensional circulation model of Lake Michigan, based on the Princeton Ocean Model (POM) and driven by observed winds. Because measurements of surface level are not available, we require that the point-wise update to the forecast horizontal current does not change the forecast surface level. This requirement makes it possible to represent the current updates by a stream function. Given an appropriate covariance model of this stream function, the current updates are calculated by kriging interpolation using the observations and the corresponding model forecast. It is further required that the current updates do not create cross-shore flows; this is represented by the stream function being constant along the coastline and is enforced by incorporating pseudo coastal data into the interpolation. This eliminates the need to construct complex spatial covariance models for the stream function. The method also accommodates observational errors. Results show that the method successfully melds observations into the model, and the influence of data assimilation propagates in space and time.
OS52A-06
Louisiana Shelf Hypoxic Zone Mixing Rates determined from Radium and Radon
Hypoxic conditions are observed in bottom waters of the inner continental shelf off the coast of Louisiana during the summer months when spring floods from the Mississippi River and fewer frontal storms create a stratified coastal system. Hypoxia is established after spring phytoplankton blooms when organic matter sources to the sediments are high. Decomposition of this organic matter supplied from the overlying water column and from underlying sediments consumes more oxygen than is produced or supplied via water mass mixing. Models have shown oxygen concentrations to be very sensitive to the mixing rate. We use naturally occurring isotopes of radium, 224,223,228,226Ra (t1/2 = 3.6 d, 11 d, 5.7 y, and 1620 y), and radon, 222Rn (t1/2 = 3.8 d), to calculate the mixing rates across the boundary of oxygenated surface water and the bottom hypoxic zone. We determine an eddy diffusion rate of 3.8 x 10-4 to 3.5 x 10-5 m2/s. This rate is greater than what was previously used in models of the open ocean, but may be of a similar magnitude to near- bottom vertical eddy diffusivity. A higher mixing rate requires great consumption of oxygen to maintain the hypoxic conditions. This suggests the hypoxic conditions may be more sensitive to organic matter input (i.e. nutrient supply) than previously thought.
OS52A-07
Comparison Between Numerical Simulations and Drifter Observations of the Surface Circulation in the Adriatic Sea
Eulerian statistics computed from drifter data and estimated from numerical simulations of circulation of the Adriatic Sea are compared for different seasons and wind forcing. The periods of interest are August-October 2003, May, June and February 2003, where drifter data have high density. The numerical simulations were performed with a 1.2- min resolution DieCAST Ocean Circulation Model adapted for the Adriatic Sea. The simulations resolve the mesoscale variability because the grid size falls below the first baroclinic deformation radius (about 5-10 km) and the model has very low horizontal dissipation. The DieCAST model is initialized with seasonally averaged temperature and salinity data and forced with climatological winds and surface buoyancy fluxes (both heat flux and evaporation minus precipitation). River discharges are varied daily according to a perpetual year for every river, and the open-boundary conditions at Otranto Strait are obtained by nesting in two larger-scale models (Cushman-Roisin et al., JGR, 2007). In the period of interests the model was forced with the COAMPS wind stresses and heat fluxes. Mean Kinetic Energy (MKE) and Eddy Kinetic Energy (EKE) estimates were obtained using the methodology commonly used with drifter (Poulain, JMS, 2001). The surface drifter observations were obtained in 2002 and 2003 as part of the DOLCEVITA project (Ursella et al., JGR, 2006). More than 120 CODE drifters were released in the northern and middle Adriatic with the purpose of studying the surface circulation at mesoscale to seasonal scale in relation to wind forcing. Drifter velocities were low-pass filtered to eliminate tidal and inertial currents. Comparison of the MKE and EKE computed from the model and drifter data shows a good agreement for high- energy dynamics along the Italian coast and local effects of strong winds like Bora and Sirocco. Discrepancies between the drifter-based and model-inferred Eulerian statistics originates in the specification of the present version of the model, i.e., its vertical architecture does not allow to resolve adequately the thin surface layer. In this connection, drifter observations provide valuable data allow improving and tuning circulation models. http://www.ogs.trieste.it
OS52A-08
Influence of Deep Navigational Channels on the Hydrodynamics and Water Quality of Shallow Coastal Basins
Shallow coastal basins throughout the world are increasingly subject to the influences of human population expansions which often bring commercial ocean-going shipping into the basins requiring the dredging of deep navigation channels. There is usually environmental concern as to the effects of such channels on the parameters of the basin which are important to its water quality and ecology. In this paper we review some of the fundamental processes that may be affected by deep navigational channels including tidal or wind driven flow, and density forced currents from salinity gradients. Our approach includes a set of scaling analyses and detailed numerical simulations based on the DHI three dimensional flexible mesh model MIKE-FM. We conclude with a set of tables that review the modeled influence on various types of bays and estuaries of a variety of navigation- channel geometries.