In response to the Announcement of Funding Opportunity by the CSCOR/COP South Florida Ecosystem Restoration Prediction and Modeling Program (SFP) we conducted a two year study of the circulation and exchange processes that regulate the residence times and flushing rates within the NE basin of Florida Bay (Fig. 1). This project was conducted through CIMAS, Task 3, Theme 3: Coastal Ocean Ecosystem Processes. The overall goal was to improve understanding of the effects of modifying fresh water supply to the Everglades as part of Everglades restoration plans. It was uncertain how proposed changes in water delivery, with increased fresh water flows to Shark River and Taylor Slough would affect salinity variability within Florida Bay. The primary objectives were to quantify the circulation and exchange rates influencing salinity variability in the eastern regions of the Bay that directly receive fresh water discharge from a series of small rivers along the northern border (Fig. 1) and to determine their interactions with connecting regions, as well as to identify the controlling physical processes. This information is needed to aid evolution and evaluation of hydrodynamic models for prediction of future water deliveries.
Fig. 1. Measurement strategy for the northeast basin subregion of Florida Bay including mooring locations for current, temperature and salinity, moored bottom pressure, sea level, drifter release sites and vessel survey track.
The measurement strategy for the NE Basin represented a continuation of our study of inner basin processes initiated with investigation of Whipray basin in the central bay. We employed similar observational techniques as were developed for the Central Basin. Observational methods will consist of a combination of Eulerian and Lagragian measurements, rapid shipboard surveying and ADCP transects to directly measure the volume and salt transports and changes of basin average salinity needed for salt balance estimates and exchange rates. Thus the measurement program is designed for determination of seasonal changes in basin salt balance and exchange patterns. The proposed effort is highly coordinated with ongoing and planned projects that will place the local basin dynamics in the context of the larger Bay-wide processes, as well as the entire south Florida coastal system to better understand the linkages over different scales, which are important to management and restoration of the south Florida coupled ecosystems.
Understanding the circulation and exchange of Florida Bay interior basins and connecting regions, and the fate of fresh water discharges from the Everglades, requires a combination of different observing techniques. High-resolution Synoptic interdisciplinary surveys are needed to determine the spatial patterns of the circulation and water mass properties during different seasons and following atmospheric forcing events, and to quantify volume and salt transports across the shallow mud banks and through the narrow connecting channels. These data are used to determine the local changes in basin-average salt content. The data are also used to estimate the advective/dispersive pathways of fresh water discharges. In-situ moored instrumentation are necessary to derive time series of volume and salt transports through the connecting channels and sea level slopes across the mud banks. These data also provide quantitative results for comparison with hydrodynamic models. Lagrangian drifters are necessary to determine the circulation patterns within the basins and to estimate advective/dispersive time scales and patterns. Due to the shallow depths involved special small-size drifters using GPS and and satellite data transmission have been constructed for this purpose. Wind and sea level data are needed for analyses with in-situ current meter and bottom pressure records for understanding the response of the interior basins and adjacent waters to wind forcing. These data are available from the ENP monitoring stations and local CMAN/Seakeys stations.
The observational program focused on the northeast basins defined by the region east of the Black Betsy Keys, west of Blackwater Sound and north of Upper Cross Bank (Fig. 1). This region receives the fresh water discharge from Taylor Slough and Trout Cr. along the northern boundary and displays large seasonal changes in salinity, with minima in the fall and strong spatial gradients that tend to coincide with bank bathymetry. Intense two-month studies were conducted during the wet season of 2002 (Sept. 7 – Nov. 18, 2002) and dry season of 2003 (Apr 2 – June 2, 2003). An in-situ array of moored current, conductivity, temperature (CT) and bottom pressure recorders was deployed for these two month periods during wet season and dry seasons (Fig. 1).
Fig. 2. Satellite photograph of the North-Eastl Basin subregion of Florida Bay and surrounding shallow mud banks (light brown).
Synoptic salinity surveys of the entire Florida Bay were conducted monthly from the R/V Virginia K using a continuously recording thermosalinograph. Each survey was completed in two days, one day for the outer portion of the bay and one for the inner area (Fig. 2). We anticipate that the primary exchange routes for the NE basin will be the openings between Russell and Manatee Keys in the southwest, and between the eastern end of Upper Cross Bank and Key Largo at Hammer Pt. in the southeast part of the basin. Current meters and CT recorders were placed in these openings to construct time series estimates of volume and salt transports. Volume and salt transports through the openings were also measured using our catamaran small boat survey vessel equipped with a 1200 kHz ADCP mounted forward of the hulls and continuous measurement of CT and Chl with a flow-through pumping system. The shipboard derived transports are used to calibrated and convert the moored data into volume and salt transport time series (uS), which is needed for the salt balance calculation. Shipboard transects were conducted several times per day over 3-day periods and repeated bi-weekly during each 2-month experiment.
Data (Florida Bay NE Basin Project)
Deployment Period #1 NE Basin Wet Season: Sept 7 – Nov 18 2002
Deployment Period #2 NE Basin Dry Season: April 2 – June 2 2003
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