National Aeronautics and Space Administration

National Climate Assessment

NASA National Climate Assessment (NCA) Activities

NASA Indicators Solicitation Proposals

Development and Testing of Potential Indicators for the National Climate Assessment

Lead PI and Center: Scott Sheridan, Kent State University
Title: Development of a Water Clarity Index for the Southeastern U.S. as a Climate Indicator

Coastal ecosystems of the Southeastern United States are sensitive and inherently linked to acute and long-term perturbations in climate. This is evident in the environmental responses to various weather-related events that affect the region such as heat waves, cold air outbreaks, tropical cyclones, and other heavy precipitation events. These phenomena affect many aspects of water quality across the Gulf, including transport, rapid cooling, eutrophication, and resuspension in shallows such as Florida Bay, and land gain/loss along the Louisiana coast. Of remotely sensed variables, water clarity, as measured by the light diffuse attenuation coefficient (Kd), can be considered to be one of the most fundamental indicators of ecosystem health. However, although Kd is available from existing satellite ocean color products, there is a lack of effective means to interpret and use it at synoptic coastal scales, especially on how to link it to climate variability. Hence, the proposed objectives of this research are:

  1. To develop a multi-decadal indicator of water clarity (Kd index) for the coastal waters of the Gulf of Mexico and Florida's Atlantic coast,
  2. To assess how high frequency (daily- weekly) perturbations and long-term changes in atmospheric conditions (circulation patterns, weather types, and precipitation events) are associated with variability in the Kd index , and
  3. To develop an empirical-based moving estimate of water clarity and light stressed conditions for purposes of tracking and monitoring critical changes in coastal regions and assessing impacts on light-sensitive species (corals, seagrass).

Moderate resolution (1-km) ocean color data from SeaWiFS (1997 - 2010), MODIS/Aqua (2002 - present), and Coastal Zone Color Scanner (1978-1986) will be used to derive validated Kd data products, from which the water clarity index will be derived for each of several pre-defined coastal regions.   Atmospheric circulation patterns, defined through synoptic climatological methods, weather type classifications, and historical precipitation records will all be used as metrics of climate change and variability within the region. 

Research currently in progress is being conducted to establish associations between dominant synoptic weather patterns and ocean color around South Florida. The development of the relationship between water clarity along the Southeastern US coast and atmospheric conditions over the period of available data is expected to show both short-term fluctuations as well as long-term trends. These connections will provide an understanding of where the Kd-climate relationship is strongest to isolate areas in the Southeast sector where historical and future changes in light conditions would likely result in substantial impacts to light-sensitive species (corals, seagrass). They will also aid in the tracking and monitoring of light stress thresholds and exceedance over defined limits applicable to both the science and management end user communities as well as provide a meaningful indicator for assessing climate impacts on the coastal environment.