ADVANCED REGIONAL AND DECADAL PREDICTIONS OF COASTAL INUNDATION FOR THE U.S. ATLANTIC AND GULF COASTS Grant uri icon

abstract

  • We must better understand and predict coastal evolution to manage the possible consequences of sea-level rise and changes in tropical cyclone activity. Sea-level rise cannot yet be predicted with confidence using models based on physical processes, because the dynamics of ice sheets and glaciers and to a lesser extent that of oceanic heat uptake are not sufficiently understood. As a way around this problem, semi-empirical approaches to projecting sea-level rise are now widely accepted, which forecast much higher sea level rise for the twenty-first century than the IPCC AR4. These projections must be complemented with regional estimates of coastal inundation for effective adaptive decision-making by planners and managers. Past and present sea-level changes reveal large regional variability due to glacial isostatic adjustment (GIA) of the solid Earth, gravitational and rotational changes driven by the exchange of mass between oceans and ice sheets, ocean density (steric) changes from temperature and salinity variations, and other factors. Further, there is little sound statistical basis for inundation from tropical cyclone landfalls because instrumental records are limited for extreme and relatively rare events. In this proposal we will produce new decadal semi-empirical projections of sea-level rise calibrated from observations of both tide gauges and proxy methods. These provide the length of time series necessary to isolate and interpret the climate component and place the more recent changes in context. We have carefully chosen five regional study areas (Connecticut, New Jersey, North Carolina, Georgia and Florida) to address spatial variability of sea-level rise along the Atlantic Coast of the United States. We will couple the regional sea-level rise projections with simulated hurricane climatology outputs and storm surge models to determine probabilities of inundation at multi-year to multi-decadal timeframes. The proposal has five major goals: 1. High-resolution relative sea-level reconstructions spanning the past 2000 years will be obtained using historical and geological data. We will reconstruct sea-level changes with unprecedented vertical resolution (?0.1-0.3m) from salt marsh sediments using microfossil-based transfer functions. By combining this new approach with a suite of complementary dating methods we will precisely constrain the chronology (decadal to centennial age resolution) of subtle changes in sea level through known climate deviations such as the Medieval Climate Anomaly, Little Ice Age and 20th century warming. 2. We will decontaminate the historical and geological sea-level data for GIA using an ensemble of geophysical models. We will identify the steric component of the historical data using hydrographic profile data from the World Ocean Database. To estimate the steric effect for the geological data we will reconstruct the behavior of mean sea level using reconstructions of land and ocean temperature as drivers. The resulting records will allow us to fingerprint ocean mass changes driven by the Greenland (GIS) and Western Antarctic Ice Sheets (WAIS). When an ice sheet melts, its gravitational attraction is reduced and sea-level rise is greater in areas geographically distal to the melting ice sheet. The melting of the GIS produces a significant latitudinal gradient in the magnitude of sea-level rise from north to south along the US Atlantic coast, whereas the influence of WAIS melting is spatially uniform. 3. Semi-empirical model describe the close link between global sea-level changes and global temperature with two terms: the fast response due to heat storage in the ocean mixed layer; and a slow response from the deep ocean and ice sheets. This approach is unlikely to suffice when considering geological data, since the deep ocean and a sizeable fraction of continental ice are expected to

date/time interval

  • September 2011 - August 2015