MTI satellite image: Information derived from this satellite image taken June 27, 2000, was used to create data maps depicting temperature and chlorophyll levels in this portion of Willapa Bay, Washington.

The transport of carbon-containing material from the river to the sea may be a critical component of Earth’s carbon cycle that could be significantly affected by subtle changes in climate. To better understand the role of rivers and estuaries in the carbon cycle and the potential long-term effects of climate change in these systems, the Pacific Northwest National Laboratory (PNNL), a Battelle-managed Department of Energy (DOE) laboratory, is coupling high-resolution remotely sensed images with circulation and transport models to create cost–effective tools for assessing the potential impact of resource management decisions.

Effective models require high-quality datasets of environmental information, e.g., data on depth, temperature, salinity, nutrients, and other water-quality indicators, such as chlorophyll and suspended particulate matter. Procuring adequate data through field sampling can be cost prohibitive. PNNL scientists are investigating the use of satellite imagery for quantifying chlorophyll concentrations to make transport estimates of chlorophyll-containing material and to quantify nutrient budgets of water bodies.

Willapa Bay, a region on the southwest coast of Washington that has supported a century of shellfish and fin fisheries, was selected for the test study. Recently named the most productive estuary in the lower 48 states, the area is a mixing zone of fresh and saline waters rich in many relevant physical, chemical, and biological processes. Satellite imagery provided band-specific radiance data that identified temperature changes, chlorophyll-a, and suspended sediment. Analysis of the variation in chlorophyll readings identified “hot spots” of rooted vegetation (e.g., eelgrass), deposited matter, and areas of free-floating, chlorophyll-containing material, such as phytoplankton.

Two particular challenges confronted the project:

• Use of the Multispectral Thermal Imager (MTI) satellite, a specialized DOE R&D satellite that provides high-resolution images, which is relatively new and does not yet have fully developed algorithms for estimating surface water temperature and chlorophyll concentration; and
• Reflectance of bottom material in the shallow waters of Willapa Bay proved problematic in the interpretation of imagery. Data derived from the imagery analysis were incorporated into tidal-driven circulation models and further used to simulate rates of growth of submerged aquatic vegetation, such as eelgrass, under varying light and temperature scenarios.

The use of data from satellite imagery analysis in coastal circulation and transport models can be a cost-effective tool to assess the potential impacts of resource management decisions. Water-quality data derived from remote sensing complements in situ monitoring, dive surveys, side-scan sonar, videography, and other visualization tools. This method also provides cost-effective repeatability and a comprehensive spatial view of physical and biological processes.

For additional information, contact Lyle Hibler at 360-681-3616, lyle.hibler@pnl.gov.