BEACHES AND COASTAL MARSHES OF THE NEW YORK METROPOLITAN REGION: ASSESSING CONSEQUENCES OF SEA-LEVEL RISE

Future sea level rise (SLR) will magnify physical hazards facing an already highly-stressed shoreline. Regional sea level has steadily climbed by 22-39 cm during the 20th century. An additional 24-108 cm SLR is projected by the 2080s, based on historic trends and climate model simulations (Hadley Centre, UK and Canadian Centre for Climate Modelling and Analysis). The return interval of the 100-year storm flood would drop to once in 60 to 4 years, on average, by the 2080s, even without changes storm climatology. Increased rates of beach erosion would necessitate up to 25% additional sand replenishment by volume. Several salt marshes of Jamaica Bay, Queens, New York, have shrunk 12% in area between 1959 and 1998. Even more extensive losses over the whole Bay during the last two decades have recently been mapped by the New York State Department of Environmental Conservation. Historic SLR alone cannot explain the accelerating trends. Low accretion rates due to a sediment deficit could be a key element; other proposed factors include erosion due to previous dredging, wave action, and waterfowl grazing. These marsh losses provide an early warning of the consequences of future coastal inundation.

In further work, we plan to refine our SLR estimates by incorporating high-resolution topographic and land-use data into finer-scale regional climate models. Potential changes in storm frequency and intensity, derived from the GISS Storm Track Model, will be used to improve flood height estimation. Accretion rates will be measured on sediment cores at several sites, using geochronological and sedimentological techniques. This information will provide a critical biogeophysical framework for conservation of remaining coastal resources in the face of climate change.