Quantifying Sargassum Boundaries on Eastern and Western Walls of the Gulf Stream Protruding Near Cape Hatteras into Sargasso Sea

• Main Authors: Brumfield, Andrew, George, Robert Y., Hayden, Linda B.
• Format: Still Image
• Language: unknown
• Published: figshare 2017
• Subjects: Distributed Computing; FOS Computer and information sciences; 80501 Distributed and Grid Systems; Applied Computer Science; Computer Software; 80505 Web Technologies excl. Web Search; North Atlantic
• Online Access: https://dx.doi.org/10.6084/m9.figshare.4522517.v1; https://figshare.com/articles/poster/Quantifying_Sargassum_Boundaries_on_Eastern_and_Western_Walls_of_the_Gulf_Stream_Protruding_Near_Cape_Hatteras_into_Sargasso_Sea/4522517/1

The Sargasso Sea has been a marine life habitat for millions of years located in the North Atlantic Subtropical Gyre with the western wall formed by the north and the north-eastern flowing, powerful ‘Gulf stream. The importance of the Sargasso Sea is recognized for the role of this current-system providing shelter and protection for marine animals such as fish and sea turtles. Two species of Sargassum natans and S. fluitans are highly branched with thalluses with numerous pneumatcyst that contain oxygen, nitrogen, and carbon dioxide to give buoyancy to the brownish algae. Sea surface winds make Sargassum aggregate and form lengthy windrowed rafts to propagate. As the pneumatcyst lose their gasses, Sargassum can reach 100 meters below the sea’s surface or even accumulate on the sea floor. Accurate mapping of the boundary in the local area of the Gulf Stream near the coast of Cape Hatteras extending to the Bermuda area has yet to be conducted using Earth observing Landsat satellites. Detection of these scattered aggregations of floating Sargassum suggests that this brown algae form small raft like sea surface features In relativity to the resolution of Landsat series and Moderate Resolution Imaging Spectroradiometer (MODIS) atmospheric instruments have been found to have difficulty due to lack of spatial resolution, coverage, recurring observance, and algorithm limitations to identify pelagic species of Sargassum. Sargassum rafts, when identified, tend to be elongated and curved in the direction of the wind, and warmer than the surrounding ocean surface. Satellite data utilizing simple ocean color indexes such as the Floating Algae Index (FAI) has shown advantages over the traditional NDVI and Enhanced Vegetation Index (EVI) because FAI is less sensitive to changes in environmental and observing conditions (aerosol type and thickness, solar/viewing geometry, and sun glint) and can see through thin clouds. The baseline subtraction method provides a simple yet effective means for atmospheric correction. The algorithms assisted in identifying the boundary area of the Sargasso Sea and the path of this floating Alga past Cape Hatteras into the Atlantic Ocean. The goal of this research was to identify seasonal patterns of the Sargassos boundary in the area near the Cape Hatteras coast out to the Bermuda for protection and regulation. Similar spectral bands are available on many existing and planned satellite sensors such as the Landsat series of Earth observational satellites, the NDVI and FIA concept was utilized to establish a long-term record of vegetation in the Gulf Stream near Cape Hatteras coast extending out to Bermuda. Once a base procedure for mapping locations where Sargassum occur, a new approach, possibly using drone, will be recommended to estimate accurate biomas of algal floating patches.