Those barrier islands turned out to be the longest chain in the world, 54 islands stretching 571 kilometers along the edges of mangrove forests, located south of the Amazon river mouth. What scientists had not realized was that the sand needed to replenish the islands was so abundant that the supply was able to keep up with erosion caused by high spring tides. In addition, no one looked for barrier islands there because spring tides reached as high as 7 meters, exceeding the 4 meter criteria established for barrier island formation. These islands had previously gone unnoticed because the lower resolution of past satellite images could not distinguish between mangroves and sand islands. However, in their new survey (that included the use of high-resolution satellite images), Stutz and Pilkey identified a chain of islands along the equatorial coast of Brazil. Stutz, an assistant professor of geosciences at Meredith College, in Raleigh, North Carolina, noted in a press release that the 657 new barrier islands had long existed but were either overlooked or misclassified in past surveys.įor instance, it was thought that barrier islands could not form in places where seasonal tides exceeded 4 meters. Image and caption credit: Jim Flocks, USGS. Two years after Hurricane Katrina, the islands show minimal recovery since the storm impacted this area: the beach is still severely eroded, open breaches are common, and vegetation is sparse. The barrier islands themselves also serve as important wildlife habitats. Protected waters between barrier islands and coastlines - bays, estuaries, and lagoons - serve as sanctuaries for many kinds of juvenile marine creatures. The islands are dynamic they’re built, eroded, and re-built by the actions of waves, tides, currents, and other physical ocean processes.įollowing the coastline, these islands create a barrier between the mainland and open ocean, shielding low-lying coastal areas from the direct brunt of ocean storm damage and erosion. The US has 405 barrier islands, more than any other country in the world. They’re found on all continents except Antarctica, with about 74 per cent of the islands in the northern hemisphere. Image credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC.īarrier islands are long narrow island chains made of sand and sediment. (Waves diffuse the sun’s reflection, but oil makes the water smoother, reflecting sunlight more brightly.) When this image was obtained, oil had already reached the barrier islands. Oil from the then-leaking Deepwater Horizon well is clearly visible as swirls of grey, and from the reflected sunlight. Slivers of land hugging the coastlines are barrier islands off Louisiana, Mississippi, and Alabama. An image of the Gulf of Mexico taken on June 12, 2010, by the Aqua satellite. Pilkey, were published in the March 2011 issue of Journal of Coastal Research. Results of this survey, conducted by Matthew L. Their results have also raised new insights into the formation and dynamics of barrier islands, and demonstrated a need for further study to better predict how barrier islands will be impacted by climate and sea level changes during this century. Scientists at Duke University and Meredith College painstakingly studied satellite images, topographic maps, and navigational charts to identify barrier islands across the world. The latest tally for all known barrier islands world-wide is 2,149, a significant increase from a 2001 study that counted 1,492 islands.
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