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Satellite-based Sargassum Watch System (SaWS)
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SaWS Clickable MapThe Sargassum Watch System (SaWS) is designed to use satellite data and numerical models to detect and track pelagic Saragassum in near-real time. Pelagic Sargassum seaweed (Image courtesy of Tracy Villareal) is a brown macroalgae floating on the ocean surface. Comprised primarily of two species, S. natans (Image courtesy of Amy Siuda) and S. fluitans (Image courtesy of Amy Siuda), it is abundant in the Intra-Americas Sea (IAS), the Atlantic, and along the coasts of British Isles and mainland Europe. In the ocean it serves as an important habitat for many marine animals as it provides food, shade, and shelter (from predators) to fish, shrimp, crabs, and turtles. Sargassum may serve as fertilizers for sand dunes and thus protects shoreline stability. It is also a marine resource for other uses such as biomass for food, fuel, and as a possible source of pharmaceutical materials. However, excessive amounts of Sargassum on beaches in populated areas can cause a lot of problems and they must be physically removed. Sargassum decomposition on beaches smells bad, attracts insects, and causes many environmental problems (e.g., smothering turtle nesting sites, sea turtle mortality, fish kills) and economic problems (e.g., diminished tourism). The beaches along the Texas coast have experienced Sargassum inundation events annually, and since 2001 beaching events have also occurred on many Caribbean shores in nearly every spring and summer. Sargassum beaching events have also been reported in western Africa and northern Brazil. Monitoring Sargassum distribution and abundance in the ocean in a timely fashion is of great importance for studying ocean ecology, helping fishery management, and forecasting Sargassum beaching events. The SaWS is meant to provide such a function through producing and sharing customized satellite imagery in near real-time in a user-friendly way. You may be interested in these links: Sea turtles victims of Sargassum seaweed Sargassum: The What, Where, and Why of this Seaweed Sargassum is a genus of large brown seaweed (a type of algae) that floats in island-like masses Gov’t allocates initial $5 million for removal of sargassums SaWS Clickable MapThe table below shows the four satellite sensors that are currently used in SaWS, with the first three sharing similar characteristics.
The raw satellite data are provided by the U.S. NASA and USGS. These data are downloaded and processed through a Virtual Antenna System using both standard and customized algorithms. Of particular importance are the two customized data products, namely the floating algae index (FAI) to detect floating algae and other materials on the ocean surface, and the color index (CI) to trace ocean circulation features. Floating algae often appears in images as slicks over the relatively homogeneous background in the FAI imagery, while ocean circulation patterns may be inferred from the various eddy and plume features in CI imagery. Two examples are given below.
SaWS Clickable MapCurrently, SaWS covers the entire Intra-Americas Sea, western Tropic Atlantic, and Bermuda. To facilitate visualization and navigation, the imagery products are divided into different geographic regions, for example Central Atlantic, Eastern Caribbean, Western Gulf of Mexico, Bermuda, etc. The "SaWS Clickable Map" at top of this paragraph shows the current coverage, where any region can be clicked to open a separate page unique to that region. A user may then select a specific date on the calendar, or use the “animate” function to browse through the image sequence quickly to determine the date of interest. A screenshot of a typical web interface is presented below.
SaWS Clickable MapUnder each images icon in the VAS (previous tab) there is a small GE button in the lower right corner. When this is clicked, a KML file is generated for that image. In addition, surface currents from the Hybrid Coordinate Ocean Model (HYCOM — from the National Ocean Partnership Program (NOPP)) are obtained, updated nightly, and made available via the VAS as a layer within Google Earth. Thus, both the image and surface currents can be displayed in Google Earth with a simple mouse click (see example below), thereby facilitating visualization and navigation. Within Google Earth, once a Sargassum raft is identified with latitude and longitude, current speed and direction (available through a mouse click over the current vector) near the raft can be used to predict the movement of the raft and a possible beaching time, in essence, forming an early warning system.
SaWS Clickable MapSargassum has impacted the Caribbean in so many ways. Here we show a few photographs that reveal the serious nature of the problem.
SaWS Clickable MapThis page provides links to Sargassum forecast or outlook bulletins (see bottom of this page), which are updated routinely. The bulletins started in early February 2018, and they are meant to give an outlook of Sargassum bloom probability in certain regions in the upcoming months, based on bloom conditions in previous months, and previous years. The 2018 Sargassum bloom in the Caribbean SeaIn January 2018, unusually high amount of Sargassum was caught in satellite imagery in both the Caribbean and the central West Atlantic. While the former could only be peered by January 2015, the latter represented a historical record. Based on these observations and based on the connectivity between the two regions, in early February 2018 we generated and distributed our first 1-page Sargassum outlook bulletin for the Caribbean Sea, and predicted that 2018 would be a major bloom year for the Caribbean. While the monthly bulletins can be found on the bottom of this page, the chart below shows Sargassum areal coverage for each calendar month. The images show distributions of Sargassum areal density for the most recent month, together with the same month in previous years. It is clear that 2018 represents a record-high bloom year for both the Caribbean and the central West Atlantic. The reasons behind this record-high bloom, however, are yet to be determined. If you click on any image below, it will open in a new tab at full resolution. You may click on the Google Earth icon beneath each satellite image to open the image in Google Earth.
Sargassum Outlook Bulletin, July 2018 Sargassum Outlook Bulletin, June 2018 Sargassum Outlook Bulletin, May 2018 Sargassum Outlook Bulletin, April 2018 Sargassum Outlook Bulletin, March 2018 |
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