USGS research geographer Benjamin Jones photographed this nearly century-old whaling boat in July 2007 along the Beaufort Sea coast near Lonely, Alaska. The boat was washed away to sea just a few months later. [Larger version]
Climate change and sea-level rise are already impacting coastal communities in many locations worldwide, including the U.S. west coast, Alaska, Hawaiʻi, and U.S. affiliated Pacific islands.
In the western tropical Pacific, elevated rates of sea-level rise (up to 1 centimeter/year) affect coastal infrastructure, freshwater resources, and terrestrial and marine ecosystems on U.S.-affiliated islands like the Marshall Islands, American Samoa, and the Northern Marianas. Alterations in storm patterns, contamination of freshwater aquifers by saltwater flooding, and permanent inundation by rising sea level—all fueled by climate change—threaten long-term human habitation on many of these atolls. Efforts to relocate coastal inhabitants from some low-lying Pacific Islands are already underway.
Along Arctic shores of Alaska, shoreline erosion and habitat loss are accelerating due to increasing permafrost thaw and sea ice forming much later in the year, leaving the coast more susceptible to waves and storm surge. Alaskan government agencies and land-use planners are relocating some Native Alaskan villages and critical airstrips farther inland from eroding shores, such as Kivalina on the northwestern coast.
Two photographs of Mitchell Cove beach on the west side of Santa Cruz during the 1997-1998 ENSO (El Niño Southern Oscillation) winter. The bottom photo was taken during an El Niño storm.
The U.S. west coast is vulnerable as well. In California alone, roughly half a million people and $100 billion worth of coastal property are at risk during the next century. In highly developed coastal areas such as San Francisco Bay and Puget Sound, hundreds of millions of dollars are being spent on restoration of nearshore ecosystems, which protect shorelines from erosion by waves and provide habitat for socially and economically important species. But resource managers remain uncertain whether outcomes of these efforts will be resilient to projected sea-level rise.
Because the impacts of climate change and sea-level rise around the Pacific and Arctic vary considerably, no single solution can mitigate the impacts. Coastal communities, along with federal, state, and local managers, need better scientific information and tools to plan for the particular threats they may face from saltwater flooding, shoreline erosion, and habitat loss.
Severe bluff erosion, along the southern end of Ocean Beach, San Francisco, California, including damage to the guard rail of the Great Highway (Calif. Highway 1). The severe winter erosion led to lane closures of the highway and an emergency, $5 million revetment along the base of this bluff. This storm damage occurred during the 2009-2010 El Niño, which, on average, eroded the shoreline 55 meters that winter.
Historically, simple “bathtub” models of future sea levels have assumed a static coast—one that is neither subsiding nor rising, neither retreating nor growing seaward—and they calculate future flooding based on just sea-level rise and tides, ignoring the impacts of storms. Those models cannot adequately account for the diverse influences that affect most coasts, including sediment input, how the coast is shaped, and “forcings”—atmospheric and oceanographic conditions that force the environment to change (for example, wind and circulation patterns, wave heights and directions).
Thus, in tectonically active coastlines like the U.S. west coast, USGS seeks to develop models that incorporate sea-level rise projections combined with storm impacts, as well as potential changes in wave heights and storm patterns associated with climate change.
Timber-pile bulkheads built to protect residential property from erosion at Ledgewood Beach, west side of Whidbey Island, Puget Sound, Washington. Photo by Hugh Shipman, Washington Department of Ecology. (From “Puget Sound Shorelines and the Impacts of Armoring—Proceedings of a State of the Science Workshop, May 2009” [Larger version]
We are developing rigorous research tools to understand the physical impacts that climate change and sea-level rise will have on dynamic geologic settings along Pacific and Arctic coasts. This research covers an enormous range of coastal settings: from permafrost coasts, to the Puget Sound estuary, the California coast, and low-lying Pacific atolls.
By understanding the effects of extreme storms, including coastal flooding, changes in the shoreline, and movement of sediment, we can develop better models for understanding long-term vulnerability of sea-level rise in various coastal settings, and help coastal managers and businesses plan for a changing climate.
On March 2, 2014, a combination of unusually high tides and large swells flooded many areas within the Republic of the Marshall Islands. Seawater regularly topped the manmade perimeter berm on the island of Roi-Namur and covered large areas of the adjacent land surface. Inset shows location of photograph taken by Peter Swarzenski, USGS.
Collaborators include USGS Coastal and Marine Geology Program colleagues in Woods Hole, Massachusetts, and St. Petersburg, Florida, and researchers with the USGS Western Ecological Research Center on Mare Island, California. Academic collaborators include those from University of Hawaiʻi, Oregon State University, University of Alaska, University of California, Scripps Institution of Oceanography, and University of Cantabria (Spain). Also involved are colleagues and federal partners from such agencies as the U.S. National Park Service, U.S. Fish and Wildlife Service, U.S. Department of Defense, and National Oceanic and Atmospheric Administration.