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Figure 2. National Park Service figure and caption: Generalized summary of harrier island dynamics and migration (vertical scale exaggerated). Stage 1 is a hypothetical barrier island with a well-developed dune line, or series of dunes, and a forest behind. In stage 2, the sea level has risen slightly and storms have knocked the dune barrier back into the woodlands. By stage 3, much of the barrier island has been overwashed and the dunes pushed back. The marsh has grown vertically and been somewhat eroded, and some former uplands are now salt marsh as a result of sea level rise. In stage 4, the barrier has retreated considerably from its original position. Dune and overwash sand has moved completely over the old forest, which is now exposed on the ocean side. Marshes near the island interior have been covered as well. Further retreat places sand completely over the original marsh surface and into the lagoon behind, where new marshes form. At stage 6 an inlet has opened and a typical tidal delta has appeared behind it. The temporary inlet has closed in stage 7, and the tidal delta now supports salt marsh and low dunes. Overwashes have tied the marsh islands to the main barrier and have filled in the old channels in stage 8. The salt marshes are now well developed on the old tidal delta, woods have grown upon the low dunes on these marsh islands, the salt marsh fringe behind the barrier is expanding, and on the barrier itself new dune lines and woodlands have formed where only a time ago there was water.

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About the author: Brenda Ekwurzel is a senior climate scientist and assistant director of climate research and analysis at UCS. She has expertise on many aspects of climate variability including Arctic Ocean and sea ice, wildfires, groundwater, and coastal erosion. She holds a Ph.D. in isotope geochemistry from Columbia University (Lamont-Doherty Earth Observatory). See Brenda's full bio.

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