1234 Long-term Acoustic Monitoring of Environmental Parameters in Estuaries M. Badiey, L. Lenain, K-C. Wong, R. Heitsenrether, A. Sundberg College of Marine Studies University of Delaware Newark, DE 19716 E-Mail: badiey@udel.edu Abstract- Coastal environment is controlled by a complex interaction of physical, chemical, biological, and geological processes. Physical processes are responsible for controlling the transport and distribution of all dissolved and suspended matters in coastal waters. A comprehensive understanding of these processes is crucial to the design and implementation of management strategies that track ecosystem health and protect coastal and estuarine waters from environmental and ecological disasters. To characterize the temporal processes occurring in the ocean, new types of infrastructure equipped with novel techniques, such as acoustical tomography, to facilitate cutting-edge oceanographic research are needed. These methods are capable of providing long-term, high- resolution observations of critical environmental parameters. I. INTRODUCTION The concept of Global Ocean Observing System has attracted attention and call for support from the international community in recent years. A few high profile international conventions have called for the establishment of such a system. On the US national level, the recent report of the National Research Council calls for the development of integrated ocean observing systems; both the executive and legislative branches of the government have become increasingly cognizant of the need for offshore and nearshore environment monitoring. Physical processes in coastal and estuarine waters often carry significant spatial and temporal variability. The large spatial variability is a direct result of the complex bathymetry and geometry often found in these waters. The temporal variability stems from the fact that coastal and estuarine waters respond to a variety of forcing mechanisms over a broad spectrum of time scales, ranging from short-period tidal motions to long-period motions induced by wind and river discharge events [1]. Historically, marine scientists have relied on in-situ measurements to examine the circulation pattern and the distributions of physical properties such as temperature and salinity. Unfortunately these conventional means of observation typically cover either intensive, but short-term observations or long-term observations with very limited spatial resolution. In recent years remote sensing methods have gained increasing recognition for their potential in measuring the distribution of water properties. Most of the currently available remote sensing techniques, however, are limited to detecting features that appear on the surface. There is a critical need for the development of innovative remote sensing technologies that measure physical properties within the water column. Acoustic methods represent an excellent example of such technologies that can be used in complex coastal systems. This paper presents the preliminary results of a monitoring station established in the Delaware Bay estuary for the purpose of providing real-time data to the community. These data can be used for variety of different purposes such as managing the health of the ecosystem based on selected measurements, to aid for mariners and shipping traffic. In addition the feasibility of using broadband acoustic tomography to provide cost-effective acoustic- based monitoring of the physical processes in coastal and estuarine waters is provided as an example of the versatility of this observing system. While broadband acoustic signals can be used to measure a wide range of physical parameters in coastal regions, the focus of the present study lies in the determination of current fluctuations in the lower Delaware Bay using such techniques. A combination of data derived from conventional oceanographic sampling platforms and broadband acoustic wave propagation measurements is reported. II. DELAWARE BAY OBSERVING SYSTEM (DBOS) As a major step toward accomplishing predictive capabilities, a number of Coastal Ocean Observing Systems have been deployed in North East states such as the Chesapeake Bay Observing System (CBOS) operated by the University of Maryland, the Long-term Ecosystem Observatory (LEO-15) located offshore of Tuckerton, New Jersey, operated by Rutgers University, and the Physical Oceanographic Real-Time System (PORTS) operated by NOAA in the Port of New York and Delaware Bay. Figure 1: Map of the Delaware Bay and the two lighthouses in DBOS, (1) Elbow of Cross Ledge lighthouse, (2) Fourteen Foot Bank lighthouse. Also shown is the location of the Rutgers’ LEO-15 coastal observatory in New Jersey and the CBOS network in Chesapeake Bay. The Delaware Bay Observing System (DBOS), operated by the University of Delaware, consists of a series of lighthouse-based platforms located along the lower and middle reaches of Delaware Bay. At each lighthouse, the platform (node) is equipped with instrumentation to provide long-term, real-time observations of oceanographic and meteorological parameters. The node is modular in design 1 2