Alaska’s waters are home to some of the world’s most productive commercial fisheries, harvesting species like pollock, cod, halibut, salmon and crab. These fisheries produce more than 60 percent of all seafood harvested in the United States, playing a critical role in both the local and national economies. The seafood industry is Alaska’s largest private employer, providing jobs for over 48,000 workers and contributing approximately $6 billion annually to the state’s economy. Nationally, it generates an estimated $15.8 billion in economic value and supports around 81,100 full-time-equivalent jobs across the country as seafood moves from ocean to table. Given the scale and importance of this industry, monitoring Alaska’s marine ecosystems is essential to ensuring long-term economic and environmental stability.
Offloading frozen Pacific cod from a catcher-processor vessel in Dutch Harbor, Alaska. Credit: NOAA Fisheries / Paul Hillman.
Low Earth orbit (LEO) satellites are vital for observing ocean conditions in high-latitude regions like Alaska. Orbiting the Earth from pole to pole, LEO satellites provide frequent and consistent coverage over Arctic regions, making them especially valuable for monitoring remote marine environments. Among these is NOAA’s Joint Polar Satellite System (JPSS), equipped with the Visible Infrared and Imaging Radiometer Suite (VIIRS).
VIIRS measures sunlight that is reflected or scattered back through the water column. Ocean color algorithms process this data to estimate key indicators of ocean composition and health, such as turbidity, chlorophyll concentration, and other optical parameters. These indicators offer important insights into fish abundance and behavior, which helps fisheries managers make more accurate stock assessments and plan sustainable and effective harvests.
Suspended solids can reduce light penetration in the water, limiting the growth of submerged plants and other photosynthetic organisms like algae that serve as habitat and food for marine life. Monitoring ocean conditions, including water clarity, sediment load, and biological productivity, provides essential data to guide sustainable fisheries management.
However, monitoring Alaska’s waters presents challenges. Arctic and subarctic waters are more optically complex than those at lower latitudes. Higher amounts of suspended sediments, dissolved organic matter, inorganic particles and other materials from thawing permafrost and glacial melt significantly influence the way light interacts with water. As land and sea ice freeze and thaws, the concentrations of these substances fluctuate, creating a continuously dynamic and complex environment. This variability makes it more difficult to retrieve accurate ocean color data, as conventional algorithms are designed for open ocean conditions and are not fine-tuned to the unique and variable optical properties of Arctic and subarctic coastal waters.
That’s why researchers at the U.S. Naval Research Laboratory (NRL) and the University of California San Diego are developing adaptive algorithms that can adjust to fluctuating conditions. The adaptive algorithms process and analyze ocean color data from VIIRS and other LEO satellite sensors to estimate concentrations of suspended particulate matter (SPM) and particulate organic carbon (POC). The ratio of POC to SPM indicates the relative amounts of organic versus mineral material suspended in the water. This information allows the algorithms to adjust their parameters in response to changes in particle compositions, enhancing the accuracy of ocean color monitoring in high-latitude regions, helping to support Alaska’s fisheries that are important to the U.S. economy.
These visualizations show water conditions in Alaska’s Bristol Bay, which produces about 46% of the world’s wild sockeye harvest. The left image shows the Suomi NPP VIIRS Diffuse Attenuation Coefficient (Kd490) monthly product for September 1, 2021, which measures how much light in the blue-green part of the spectrum (around 490 nanometers) is absorbed and scattered in the water. Higher Kd490 values indicate lower water clarity with shallower light penetration, while lower values reflect clearer water and deeper light penetration. The right image shows the NOAA-20 VIIRS Experimental Particulate Organic Carbon (POC) monthly product for September 16, 2021. High POC often correlates with higher net primary production as phytoplankton photosynthesize and create organic matter. However, high POC in coastal areas can also be the result of river runoff or resuspended sediment that increases turbidity. Source: NOAA CoastWatch West Coast Regional Node.
LEO ocean color data help fisheries managers make better-informed decisions. By better understanding fluctuating ocean conditions, they can respond proactively to shifts in fish and aquaculture habitats or productivity. With advanced LEO instruments like VIIRS, the U.S. is better equipped to protect Alaska’s marine resources and support a seafood industry that’s vital to communities across the state and the nation.
To learn more about NRL’s adaptive ocean color algorithms, see An Adaptive Optical Approach to Ocean Color Using LEO Satellites to Monitor Arctic Waters on page 162 of the 2024 LEO Science Digest.