Coastal ocean models are used by NOAA to predict the oceanographic conditions in coastal and estuarine systems. Models are developed by the Marine Modeling and Analysis Programs (MMAP) which generate accurate simulations of water surface elevation, velocity, temperature, and salinity. The accuracy of these models is calculated by MMAP’s skill assessment software. These validated models can then be used as the basis for ecological applications that depend upon linkages between oceanographic and ecological data. The models’ ability to describe hydrographic conditions within coastal systems enables use of model output to characterize ecological processes. The resulting products based on hydrodynamic model output are used by coastal resource managers in a wide range of applications. For example, an application could describe the distribution of biota such as algae or fish larvae, or the transport and fate of contaminant plumes.
SF6 Tracer Evaluation of Modeled Currents
Determination of Residence Time in Estuaries
Residence time is a measure of the average time a substance spends within a physical system; this substance could be any particle flowing with the water. In the case of the coastal ocean a measure of residence time can be extremely useful in determining transport and fate of contaminants and organisms in estuarine systems. High resolution hydrodynamic models can be used to calculate residence time in coastal estuaries in more thorough ways than by observations alone. This methodology has been employed and developed by MMAP for ecological applications of coastal hydrodynamic models.
Harmful Algal Bloom (HAB) Forecast Guidance
Harmful algal blooms (HAB) arise in coastal waters when naturally occurring algae reproduce at an overwhelming rate (bloom) and produce negative impacts on the ecosystem. HABs can deprive fish and other wildlife of necessary oxygen in the water or can release toxins into the environment which can taint shellfish and be deadly to breathe. HABs are controlled by conditions in the water such as temperature and nutrient supply. Therefore, hydrodynamic circulation models which can model these variables are being used by NOAA to predict the likelihood of HAB occurrence. This data is then used to produce regular bulletins for coastal managers describing potential HAB outbreaks.
Chesapeake Bay Sea Nettle Distribution Forecast Guidance
The sea nettle is a nuisance jellyfish that becomes predominant in the Chesapeake Bay during certain times of the year. It causes a painful sting and therefore it limits access to the water when it becomes widespread. Its distribution in the bay is governed by temperature and salinity conditions. Therefore, its likely distribution can be calculated from hydrodynamic model output and is provided as forecast guidance by producing maps available on the Internet.
Sulfur hexafluoride (SF6) is a colorless, odorless non-toxic gas that is commonly used as a tracer in oceanographic studies by injecting it into the water and monitoring its distribution over the following days. A tracer is used to study currents, mixing, and transport within a coastal system. Knowledge of these processes is beneficial since it permits understanding of the physical processes in the system (e.g., current patterns) and the fate of contaminants. MMAP has used SF6 tracer experiments to examine the ability of coastal hydrodynamic models to predict SF6 transport released into the modeled system. Field experiments were compared to operational model output in New York Harbor and Galveston Bay.