Sea-level Rise Science and Decision Making in an Uncertain Future Rob Thieler U.S. Geological Survey Woods Hole, MA
Concepts Sea-level rise is one of the most certain impacts of climate change. There is very high confidence (>90% chance) that sea-level will rise between 8 inches and 6.6 feet by 2100. The coast does not flood like a bathtub. It's much more exciting (and challenging). Effective adaptation to rising sea level will require changing approaches to coastal management.
Past, Current and Projected Global Temperature The last 10,000 years have been ideal for the development of human societies. This has been a unique time during which climate varied very little and enabled humankind to flourish.
Sea-level rise rates since the Last Glacial Maximum mwp-ia mwp-ib Global delta initiation (Stanley and Warne, 1994) U.S. Atlantic, U.K. wetland initiation; barrier island stability (Shennan and Horton, 2002; Engelhart et al., 2009) Rate of SLR (mm/yr) Thousands of 14 C years before present (SLR rate based on Fairbanks, 1989; ice extent from Dyke, 2004)
Past, present, and potential future rates of sea-level rise Geologic past (Fairbanks, 1989; Horton et al. 2009) Projections (Rahmstorf, 2007) Instrumental record (Church and White, 2006) Rate of SLR (mm/yr) Years before present
Land water storage changes Ocean currents change Land can rise or sink Warm water expands Ice melts into the ocean (IPCC, 2001)
Global variability in SLR Loss of the West Antarctic Ice Sheet can cause up to 25% more SLR on the U.S. coast. (Eric Steig) (Bamber et al., 2009)
Regional variability in SLR (Sallenger et al., 2012) (Yin et al., 2009) Regional changes in circulation and ocean warming can increase sea level by tens of centimeters, for example in the northeastern U.S. (north of Cape Hatteras).
Importance of Spatial Scale
Importance of Temporal Scale Shoreline Position Seaward Long Term Trend Short Term Variance Time Short-term Variance (hours to decade) Storm impact/recovery Annual cycles El Niño Long-term Trend (decades to centuries) Sediment deficit or surplus Sea-level rise
Future sea-level rise: certain, yet uncertain 6.6 ft 3.9 ft 1.6 ft 0.7 ft (Parris et al., 2012) How to choose? Time horizon Risk tolerance
The coast is not like a bathtub Miami New York Boston
So, what can happen? Bluff erosion Island Breaching Listed Species Impacts Overwash Urban Inundation Wetland Migration or Loss Threshold Crossing R. Carlson Water Quality Reduction Ecosystem Change Infrastructure Failure
Sea-level rise impacts: A multivariate problem with uncertainties everywhere Driving Forces Groundwater Impact Wetland Loss Habitat Loss Climate Change & Sea Level Rise Physical & Biological Processes Coastal Erosion Potential Impacts Management Decisions Initial Conditions Inundation Safety
Informing Decisions in a Changing Climate National Research Council (2009) The end of Climate Stationarity requires that organizations and individuals alter their standard practices and decision routines to take climate change into account. Scientific priorities and practices need to change so that the scientific community can provide better support to decision makers in managing emerging climate risks. Decision makers must expect to be surprised because of the nature of climate change and the incompleteness of scientific understanding of its consequences. An uncertainty management framework should be used because of the inadequacies of predictive capability.
Decision support model uses regional datasets and their uncertainties to predict probabilities of inundation level and response type Sea Level in 2020 or 2050 (m) 0 to 0.25 100 0.25 to 0.5 0 + 0.5 to 1 0 + 0.125 ± 0.072 Latest GCM Projections Vert. Land Motion (m, rel 2010) -0.1 to 0 94.3 0 to 0.05 5.74 0.05 to 0.1 0 + -0.0457 ± 0.033 DEM elevation (m, MHW) -10 to -1 42.9-1 to 0 27.3 0 to 1 20.4 1 to 2 9.40-2.25 ± 3.3 Inundation level (m) [pos is dry] -10.3201 to -1 50.8-1 to 0 21.4 0 to 1 18.6 1 to 5 9.29-2.61 ± 3.8 Tide Gauge and GPS Velocities Land Cover (6 classes) Water 54.3 Marsh 25.6 Beach 4.87 Cliff 0.25 Forest 8.59 Developed 6.40 2.03 ± 1.5 Coastal Response Dynamic 32.6 Inundate 67.4 0.674 ± 0.47 Dynamic Response vs. Inundation National Elevation Dataset TNC Ecological Systems Map Sydney Coastal Councils Group
Mapping Coastal Change Using Bayesian Networks* Bayesian Network uses climate forcing and geologic constraints Provides scientific knowledge context for decision makers Prediction and uncertainty maps identify where better information is needed (input data, process understanding) Can use to focus research resources! *Research in progress
Mapping Coastal Change Using Bayesian Networks* Bayesian Network uses climate forcing and geologic constraints Provides scientific knowledge context for decision makers Prediction and uncertainty maps identify where better information is needed (input data, process understanding) Can use to focus research resources! *Research in progress
Objective: predict influence of sea-level rise coastal morphology plover* Sea-level change (and other factors) drives coastal erosion Erosion and sedimentation modify morphology Large-scale and local morphology predicts plover success (and vegetation, groundwater resources, wetland behavior, etc.) *The people problem is the same, minus the feathers
Integration and prediction of coastal change Short- and long-term coastal hazard processes (i.e., storms, sea-level rise) Uses data and models storm/wave models + shoreline data = coastal change prediction and prediction uncertainty + = time Shoreline change near San Francisco using Kalman filter (data assimilation) (Long and Plant, 2012)
Understanding Where We Are, and Where We Could Go www.falmouthmass.us/depart.php?depkey=coastal
Vision for Falmouth s Coast (for the next 50-100 years) Beaches and dunes wide enough for protection from storms and public access and use. Sufficient sand in the coastal system. Sustained and enhanced water quality, habitat and fisheries resources. A minimum of hard structures (groins, seawalls, etc.). Public infrastructure will be relocated from the immediate coast. A proactive approach to shoreline management to prevent problems and provide a response protocol when shoreline damage occurs.
Achieving the Vision for Falmouth s Coast Acquire coastal land for open space. Move or change vulnerable public infrastructure. Plan future infrastructure (e.g., roads, sewers) wisely. Conduct beach nourishment experiments at key source locations. Remove unnecessary, hazardous, or damaging coastal armoring structures. Create effective sand management systems. Improve regulations to protect coastal systems and beaches. Encourage protection of valuable coastal assets such as unarmored bluffs.
Summary The coast as we know it today is a product of sea-level rise Major changes are coming to the coast, ecosystems, and resources Future sea-level rise is a certain impact We have already made a commitment to several centuries of rise Future sea-level rise is an uncertain impact Rates and magnitudes poorly constrained Societal response unknown Informed preparation is important