Sound Science Background
Long Island Sound
The Long Island Sound is an estuary shared by New York and Connecticut. Its picturesque beauty supports the feeding, nesting, and nursery grounds for a wide range of plant and animal life. These qualities make the Sound a highly prized natural, economic and recreational resource for the surrounding region. In fact, recognition of the Sound’s status as one of the nation’s most important natural resources was afforded by its official designation as an ‘Estuary of National Significance’ under the U.S. National Estuary Program (NEP) in 1988. The areas surrounding the Sound are heavily urbanized, with over 8 million people living in the Long Island Sound watershed. The economic demands associated with the Long Island Sound, in addition to this urbanization, put considerable stress on the its ecological systems.
Concerns over the environmental health of the Sound have been voiced for more than three decades as evidenced by a number of state and federal programs. The most comprehensive of these programs to date has been associated with the initiation of the Long Island Sound Study (LISS) in 1985, when Congress appropriated funds to the Environmental Protection Agency (EPA) to carry out a program to research, monitor and assess water quality in the Sound in collaboration with the New York Department of Environmental Conservation and the Connecticut Department of Environmental Protection. In association with the LISS, the development of a Comprehensive Conservation and Management Plan (CCMP) was undertaken in 1988 to improve the environmental quality of Long Island Sound. The CCMP focused on five key issues: hypoxia, toxic contamination, pathogens, floatable debris, and the heath of the living resources. Hypoxia, which is defined as dissolved oxygen (DO) levels below 3 mg/l, was identified as the most pressing of the five issues. During late summer, hypoxia can develop in the bottom waters over substantial portions of the Long Island Sound. For example, over this most recent summer hypoxia developed over large portionsof western and central Long Island Sound. To provide a framework for interpreting the complex interactions between circulation, nutrient loadings, eutrophication, dissolved oxygen as well as other characteristics of the Sound, and specifically to provide a management tool for evaluating the nutrient and toxic waste reduction proposed under the CCMP, a combined circulation and water quality model, was developed by Hydroqual, Inc. for the Long Island Sound. This model is used to estimate water quality outcomes given various water/sewage management scenarios and thus is used as a guide for LIS water management decisions.
Of notable scientific importance is the fact that for an estuary, the Long Island Sound is relatively shallow and it has a large surface area. These two features make its circulation highly dependent on local atmospheric forcing (i.e., surface wind stress, air-sea fluxes of heat and freshwater). The influence that atmospheric forcing has on the circulation and vertical density stratification of the Sound has yet to be fully investigated or quantified due to the extreme paucity of over-water, in-situ meteorological measurements with accompanying observations of surface water properties. The ramifications of this are significant because coupled hydrodynamic/water quality models, such as the one developed for the LISS for making environmental management decisions (e.g., sewage outflow amount, allowable toxicity levels) must necessarily be supplied with atmospheric forcing conditions (i.e. weather and heat flux measurements). Until the development of the ferry-based observing system, these types of observations were generally unavailable to adequately meet this need. This lack of observed data has contributed to a significant uncertainty in the application and implementation of the Long Island Sound management decisions and thus compromises the viability and sustainability of Long Island Sound resources. This ferry-based research project is designed to provide these measurements and thus improve the framework that has been established for the management and care of the Long Island Sound.
A brief description of the framework, participants and sponsors of this research project are given under Joint Research Project and People & Partners. Details regarding the ferry-based observing system are given under System Description. Finally, the specific scientific issues that are to be addressed by this research project are described under Scientific Objectives. In addition, the following paragraphs describe additional benefits associated with the ferry-based observing system.
Since the fall of 1999, a huge number of lobsters have died and more than 1,300 lobstermen of the Long Island Sound have been impacted by the loss. These marine mortalities mark the third time in as many years that aquatic life-killing diseases have either directly or indirectly been deemed responsible for negatively impacting important underwater crops adjacent to Long Island. In 1997 and 1998, it was oysters and clams and, in 1999, it was lobsters. Earning a dockside value of over $29 million in 1998 according to National Marine Fisheries Service statistics, the New York lobster catch was greater than the value of all fin fish combined in 1996, 1997 and 1998. However, the mortalities associated with the 1999 die off caused this value to plummet to less than 45% of the 1998 amount. This is not the first time the lobster catch has been severely depleted. A similar event, although not as catastrophic, occurred in 1991.
A number of local agencies are now trying to uncover the reasons for these mortalities. One contender is warming associated with climate change and/or natural variability. Long Island Sound lobsters are sensitive to water temperature and dissolved oxygen, being just at the southern (i.e. warmer) edge of the cold waters that they favor. Thus, any local warming can have a dramatic influence on the health and reproduction of the lobsters. There is some indirect evidence that prior to 1999, there was a substantial warming of the local marine climate which could be ultimately responsible for the lobster die off, either through direct temperature effects or through the development of stratification (warm water overlying cold water) and the subsequent development of bottom water hypoxia (low dissovled oxygen) due to the difficulty of mixing oxygen-rich water down to the bottom. Other contenders for understanding the lobster problem involve pathogens, toxic byproducts from the surrounding urban environment, and the development of hypoxia due to the over abundance of nitrogen in the Long Island Sound associated with sewage outflow, all of which are controlled/managed to some extent by the LISS/CCMP. Unfortunately, until there are some direct over-water measurements of the physical mechanisms that effect water temperature and stratification (e.g., solar radiation, precipitation, wind mixing, air-sea heat fluxes), such as those collected from the ferry, it will be difficult to determine the role that climate is playing in this problem versus other factors which require intervention and management (e.g. sewage outflow).
Public Outreach and Education
A computer monitor is set up on the passenger deck of the ferry to provide a platform for displaying the real-time data obtained by the observing system to the passengers and crew (see System Description). The display of the data is incorporated into an educational framework that provides a brief description of the scientific and management issues associated with the Long Island Sound environment as well as the specific issues associated with the ferry-based research project. It is hoped that this forum, as well as these web pages, will provide an additional avenue for raising the general public’s awareness of environmental issues associated with the Long Island Sound. These two outreach elements, the on-board presentation and the web pages, provide unique and useful resources for environmental education. In particular, the web site can be used for readily monitoring local marine and atmospheric conditions as well as their interaction. In addition, these real-time data, as well as the archived data, could be an ideal resource for developing more in-depth environmental research projects.
Public Weather Forecasts
Weather forecast responsibility for the Long Island Sound rests upon the New York City National Weather Service Office, located in Upton, NY. Prior to the development of the ferry-based observing system, there was a near void of real-time meteorological observations over the Long Island Sound. Such data are extremely useful to forecasters responsible for producing near-term forecasts of marine conditions over the Sound as well as for verifying them. Since the project’s inception, the National Weather Service’s Eastern Region Headquarters has expressed considerable interest in the meteorlogical data collected from the ferry. In fact, they sponsored elements of the project in order to have the data transmitted in real-time to their offices so it can be utilized to improve the weather forecasts over the Long Island Sound.
Atmospheric Modeling and Research
The ferry-based meteorological measurements provide extremely useful information to Stony Brook University’s mesoscale (~20-200km) atmospheric modeling and research program. These efforts involve using numerical forecast models with nested grids that afford a spatial resolution over the local area of about 4 km to study the physical processes (e.g., wave dynamics, cloud physics, climate/weather interactions) associated with weather along the eastern seaboard as well as to provide additional numerical forecasts to augment the resources of the local National Weather Service office. As indicated above, the data void over the Long Island Sound prohibits verification of model fields and/or assimilation of data from over the Sound into the forecast model. The observations from the ferry not only provide a robust set of meteorological validation/assimilation data over the Sound, but also have the means to provide over-water estimates of the surface heat, momentum and freshwater fluxes as well. Verifying the latter is a highly discriminating test of a model’s ability to simulate the interaction between the surface and the atmosphere and thus are a valuable addition in developing this modeling and forecast system. For example, surface heat flux plays a very important role in the development of mesoscale weather systems, including diurnal variability such as daily minimum and maximum temperatures and the development of sea breezes which are quite common in this region during undisturbed periods. Ongoing and future research in regards to mesoscale atmospheric modeling that is important to the Long Island Sound is the development of high-resolution atmospheric analyses and forecasts that can be used as robust forcing conditions for Long Island Sound ocean model studies and/or forecasts of storm surge and wave height predictions.
In January 2000, a satellite ground station for obtaining a number of environmental parameters from the polar-orbiting NOAA weather and NASA SeaWiFS satellites was installed at the Marine Sciences Research Center at Stony Brook University in collaboration with the Brookhaven National Laboratory. The parameters include sea surface temperature (SST), chlorophyll-a, cloudiness, aerosol amount and atmospheric temperature profiles. The satellite SST retrievals provide a valuable source of data for initializing and/or verifying regional scale SST for Long Island Sound ocean modeling efforts as well as for supplying surface boundary conditions for the high-resolution atmospheric modeling research. The satellite-derived chlorophyll-a data, used in conjunction with the ferry observations, will provide a basis for constraining and quantifying the spatial and temporal variation of planktonic production in the Sound. At present, there are only minimal data available on primary production patterns necessary to accurately constrain models of biogeochemical cycling, including oxygen distributions, in the Sound. A detailed knowledge of seasonal surface water chlorophyll-a would represent a significant advance in our ability to define productivity distributions, to interpret the evolution of water column dissolved oxygen conditions, and to evaluate benthic remineralization and bottom community recruitment patterns.
To use these remotely sensed measurements with confidence it is necessary to have in-situ data in order to validate and/or tune the retrieval algorithms. In this regard, it is important to recognize that this validation effort must extend across a considerable range of the atmospheric and ocean conditions experienced by the region. This includes sampling at least through an entire annual cycle, and preferably longer to account for interannual variability and satellite sensor drift. The ferry-based observing system provides this in-situ data and thus a means to validate the satellite-derived SST and surface chlorophyll values so that these satellite data can be more aptly employed for the studies discussed above.