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USGS Workshop on Sea-Level-Rise Impacts Held in Menlo Park, California

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Typical wetland in Puget Sound
Above: Typical wetland in Puget Sound that now faces "squeeze" as rising sea level meets human infrastructure (in this case, levees and agricultural fields). Photograph by Eric Grossman. [larger version]

Future impacts of sea-level rise are attracting significant attention from Federal, State, and local coastal-zone managers. To identify and address these managers' needs, the U.S. Geological Survey (USGS)'s Western Region held an internal USGS workshop on Sea-Level-Rise Impacts on November 6-7, 2007, in Menlo Park, California. The meeting was attended by 30 scientists from four USGS disciplines (geology, geography, biology, and water) and 13 different science centers in the Western Region. In part a follow-up to the Western Region's Climate Change workshop held October 10-11, the November workshop focused on just one important climate-change issue in the Western Region: the impacts of projected sea-level rise. The primary goal of attendees was to identify and develop new interdisciplinary-research opportunities and collaborations on sea-level-rise impacts to coastal settings in the Western United States.

This workshop was motivated by recent Intergovernmental Panel on Climate Change (IPCC) projections of sea-level rise that range from 18 to 59 cm by the year 2100 (URL
[2.2 MB PDF]; see table SPM-2 and discussion). These estimates are commonly regarded as conservative (for example, see URL and are currently being debated. Other recent projections suggest that global sea-level rise by 2100 may range from 50 to 140 cm (for example, see URL

Workshop participants met as a group for the first morning and early afternoon to review sea-level-rise science and scenarios and to hear brief summaries of ongoing USGS work on this subject. The rest of the first day and the beginning of the second were spent in four breakout groups focused on critical scientific issues in four geomorphic areas: estuaries and wetlands, high-energy mid-latitude coasts, high-latitude coasts, and tropical coasts. Each breakout group was tasked with developing a list of key sea-level-rise issues, including uncertainties, data gaps, and needed maps and products. Breakout groups also developed preliminary conceptual models, influence diagrams (visual representations of the main features of a situation and the important relations that exist among them), and scenarios describing processes that affect change in the four geomorphic areas. This exercise served to highlight where research is needed and might be effectively integrated to examine systems that respond to multiple processes and feedbacks (for example, how sediment accumulation shapes wetland vegetation and succession, which, in turn, can influence sediment retention or change caused by bird and mammal foraging).

Breakout groups reported back to the entire workshop to collect feedback before preparing one-page summaries of project-scale scientific investigations of sea-level-rise impacts that could be pursued in the Western Region. Some of the discussion centered on short-term work and was used to refine proposals currently being prepared in response to the USGS Climate Change Request for Proposals. Other discussion was used to develop ideas for integrated science work in fiscal year 2009 and beyond. Highlights of the breakout-group discussions are summarized below.

Wetlands and Estuaries

This breakout group comprised biologists, geographers, geologists, and hydrologists who have been working in San Francisco Bay and the adjoining Sacramento-San Joaquin Delta (referred to jointly as the San Francisco Bay-Delta), Puget Sound, and the Columbia River estuary. This breakout group considered sea-level-related impacts to major urban estuaries (such as the San Francisco Bay-Delta and Puget Sound), as well as small coastal wetlands throughout California, the Pacific Northwest, and Southeast Alaska.

Key issues identified for wetlands and estuaries along the developed west coast include:

  • Loss of wetland habitat due to submergence
  • Inability of wetland habitat to migrate laterally due to human infrastructure or geomorphology
  • Wetland sediment supply, organic "buildup," and vertical accretion
  • Changes to estuarine mixing, water quality, and carbon export
  • Changes to coastal watersheds, including water supply, sediment loads, and habitats
  • Changes in habitat diversity, abundance, and distribution—especially for migratory birds and fish, many that are listed as endangered or threatened, including U.S. Department of the Interior (DOI) trust species
  • The fate of large-scale habitat-restoration projects
  • Increased vulnerability of agricultural and industrial infrastructure, especially prevalent in deltaic wetland settings
  • Assessment of mitigation options despite high hazard due to flooding and inundation
  • Cumulative impacts to wetlands associated with climate change (for example, reduced spring/summer runoff, warming estuarine surface-water temperatures)

Although some baseline data exist for marsh and wetland habitats in the San Francisco Bay-Delta, the breakout group recognized that for most west-coast marshes and wetlands, important baseline information is still needed. Importantly, "reference" wetlands and marshes (those not impacted by human activities) are virtually nonexistent along the west coast. Specific information is needed on rates of vertical and lateral accretion of sediment and wetland vegetation, rates of relative sea-level rise, habitat distribution, habitat needs of principal biotic assemblages, biogeochemical cycling, and ecosystem function and diversity.

High-Energy, Mid-Latitude Coasts of California, Oregon, and Washington

This breakout group focused on stretches of the mid-latitude Pacific coast exposed to nearly continuous wave action. Sea-level-rise impacts on these coasts can be significantly amplified by high waves; storm surges; tidal currents; interannual climate phenomena, such as the El Niño Southern Oscillation (ENSO; see "What is El Niño"); and decadal variation, such as the Pacific Decadal Oscillation (PDO; see "What is the Pacific Decadal Oscillation?").

Some important issues for high-energy coasts include:

  • Need for baseline mapping data and indicators to monitor change
  • Increased coastal inundation and storm surge as frequency of flooding increases
  • Changes in the rates of coastal erosion and shoreline retreat
  • Changes to sediment budgets, sediment transport, and deposition that will affect nearshore and shelf habitats, beach widths, recreation, and water quality
  • Implications for regional sediment management, including beach nourishment, dredging, coastal armoring, and navigation.
  • Increased vulnerability of human populations and infrastructure and assessment of mitigation options
  • Need for predictive models to predict impacts, assess risk, and provide warning systems

Typical unconsolidated bluff along the central California coast undergoing cliff retreat Above: Typical unconsolidated bluff along the central California coast undergoing cliff retreat. Retreat is especially rapid during El Niņo periods, when sea level can be elevated 10 to 20 cm above its average position for several months at a time. Photograph from Cotton, Shires, and Associates, Inc., Geotechnical Report, Northridge Bluff Landslide, Daly City, California, April 2004. [larger version]

High-Latitude (Alaskan) Coasts

Bering Glacier
Above: How coastal and tidewater glaciers, such as the Bering Glacier, shown here, will respond to sea-level rise remains uncertain. Understanding the modes and rates of change in glacier flow and freshwater and sediment export to coastal waters is essential to predicting how coastal habitats, ecosystem function, and sediment processes will change. Photograph by Eric Grossman. [larger version]

This breakout group considered issues related to sea-level rise and climate change over a wide range of Alaska's coastal provinces, including impacts to infrastructure along the Yukon Delta and the North Slope. Participants recognized that many sea-level-rise impacts in Alaska will be greatly exacerbated by the range of climate changes (air and sea temperature, sea-ice extent, winds and storms, precipitation), expected to be most extreme at high latitudes.

Important issues facing high-latitude coasts include:

  • Dramatically high rates of coastal erosion
  • Impact of diminished icecap on Alaskan ecosystems and coastal erosion
  • Changes in wetland locations and impact to migratory and DOI trust species, such as polar bears
  • Saltwater inundation of ecologically sensitive habitats for birds and mammals
  • Potentially severe impact on Native Americans' land and culture
  • Erosion and inundation of extensive habitat and infrastructure along the North Slope
  • Need for high-resolution land-surface baseline datasets for monitoring change
  • Changes in tidewater glacier dynamics, including freshwater, sediment, and nutrient delivery to coastal waters
  • Impact to nearshore and shelf habitat and marine resources
  • Feedbacks of accelerated glacier melt on coastal climates and further warming
  • Potential changes in Federally mandated management regimes for DOI lands

wellhead and pilings of the J.W. Dalton Test Well #1 in September 2004 wellhead and pilings of the J.W. Dalton Test Well #1 partially submerged in September 2005
Above left and right: The rapid retreat of Arctic tundra coastline has exposed oil-exploration infrastructure on the shore of the Beaufort Sea, subject to some of the highest coastal-retreat rates in the world. Shown here are the wellhead and pilings of the J.W. Dalton Test Well #1 in September 2004 (left [larger version]) and September 2005 (right [larger version]). Drilled in 1979 as part of USGS exploration in the National Petroleum Reserve in Alaska, the well was originally located 1,500 ft inland from the Beaufort Sea coast; it is approximately 120 mi northwest of Prudhoe Bay. Photographs by Susan Flora, Bureau of Land Management.

Tropical Coasts

This breakout group considered the impact of sea-level rise on low-latitude and tropical coastlines in the Pacific Ocean (for example, Hawai‘i, Guam, American Samoa, and the Federated States of Micronesia), with a special emphasis on the fate of coral reefs, atolls, and the commonly narrow coastal fringes of tropical islands. The U.S. Department of Defense (DOD) and Department of the Interior (DOI) maintain extensive land holdings across the Pacific region, many of which support critical wildlife and (or) defense installations within just a few meters of today's mean sea level.

Important issues for tropical coasts include:

  • Forecasting the impacts of sea-level rise on essential land areas, resources, infrastructure, and social systems
  • Inundation of communities and infrastructure in narrow coastal fringes and over entire atolls; disruption and relocation of entire populations and cultures; loss of cultural resources
  • Changes in physical processes on coral reefs (including water circulation, sediment dynamics, sediment resuspension by waves, and erosion by waves) due to higher sea levels
  • Identification of at-risk habitats, species, and populations
  • Saline intrusion of coastal aquifers and coastal freshwater and brackish habitats

coral-reef systems Funafuti atoll
Above left: Many coral-reef systems are already undergoing increases in sediment impact caused by land use. Uncertainty remains as to how sea-level rise will influence the coastal processes, including sedimentation, that affect coral-reef growth. Photograph by Michael Field. [larger version]

Above right: Funafuti atoll, capital of the island-nation of Tuvalu, midway between Hawai‘i and Australia. Continuing sea-level rise could have serious consequences for such low-lying islands, and could be compounded by other possible effects of climate change, such as an increase in the intensity of extreme storms. Thin freshwater lenses are also under serious threat from rising seas. Photograph taken in 1986 by Bruce Richmond. [larger version]

Taking the Next Steps

The many impacts of sea-level rise identified in the workshop will be addressed in several ways, by using existing scientific methods as well as newly developed technology and by conducting new research efforts in mapping, monitoring, and modeling. Some of the methods to be employed include:

  • Integrating projected sea-level rise and geodynamics (for example, tectonic uplift, subsidence, and isostatic rebound) to develop region-specific sea-level projections
  • Identifying mapping data (for example, topography, bathymetry, habitats, and hazards) needed to address sea-level-rise issues
  • Identifying effective mapping tools and approaches to mapping and detecting change, including mapping across the onshore-offshore boundary
  • Modeling ecosystem changes, including species changes, ecosystem sensitivities, and change thresholds
  • Developing integrated natural- and social-science models that quantify risks to populations, infrastructure, and ecosystems
  • Developing tools for DOI land managers to help them assess options in view of likely economic and environmental consequences

The Sea Level Rise Impacts Workshop was convened by Sam Johnson (Western Coastal and Marine Geology Team [WCMG]), Tom Suchanek (Western Ecological Research Center), Kim Taylor (California Water Science Center), and Len Gaydos (Western Region Geography) and led by Eric Grossman (WCMG). Serving on the organizing committee were Grossman, Ann Gibbs, Bruce Richmond, and Jane Reid (all WCMG).

USGS employees can view additional information about the workshop—including the breakout groups' one-page summaries and a list of all attendees' names and e-mail addresses—on the USGS internal Web site; visit URL and search the USGS Intranet for the phrase "Sea Level Rise Impacts Workshop."

Thanks to all the participants for a stimulating workshop!

Related Sound Waves Stories
Expert Panel Discusses Potential Impacts of Future Sea-Level Rise on U.S. Mid-Atlantic Coast
July 2007

Related Web Sites
Global Climate-Change Resources
American Association for the Advancement of Science
The IPCC sea level numbers
RealClimate, a commentary site on climate
A Semi-Empirical Approach to Projecting Future Sea-Level Rise

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Earthquake Damage Near Nuclear Power Plant

Coastal Processes Affect a Restored Tidal Wetland

Coral-Reef Investigation Featured in Molokai Times

Outreach Open House at FISC St. Petersburg

Meetings Workshop on Impacts of Sea Level Rise

International Delta Roundtable Meeting

2007 SACNAS National Conference

Ocean and Coastal Mapping Inventory Workshop

Awards Biologists Honored for Polar Bear Research

Brian Atwater Receives Award, Elected to National Academy of Sciences

Peter Barnes Receives Scientist Emeritus Best Publication Award

Ralph Cheng Receives Distinguished Service Award

Janet Thompson Receives Diversity Award

Staff Samples on the Move

Runners Team Up for Marathon

G.K. Gilbert Helps Celebrate Alumni Reunion


New Book on Tidal Freshwater Forested Wetlands

Jan. / Feb. Publications List U. S. Department of the Interior | U.S. Geological Survey
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