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2o d, 7 i r�trwe GIr'�Ib( '7I Results of climate models suggest that mean sea level rise during this century will significantly exceed rates experienced over the past century. Based on temper- ature increases projected in the IPCC report of 2 - 11.5 °F of warming over the next century, global sea levels could rise from 0.18 meters to 0.59 meters, with an additional increase of up to 0.2 meters based on melting ice sheets (Meehl et al. 2007). Since publication of the Fourth IPCC report, these esti- mates have been called conservative (e.g., velicogna and Wahr 2006, Bamber et al. 2009). The IPCC projections include a conservative contribution from the Greenland and Antarctic ice sheets and glaciers at the rates observed for 1993 -2003 (Meehl et al. 2007). However, scientists have been warning of accelerations in the ice sheets and near - coastal thin- ning for several years (Rignot and Thomas 2002, Thomas et al. 2004, Rignot and Kanagaratnam 2006, Csatho et al. 2008). In particular, Rignot and Kanagaratnam (2006) detected a doubling in mass loss in the Greenland ice sheet between 1996 and 2005 using satellite radar interferometry and found that the contribution of Greenland's melting ice to sea level rise increased from 0.23 ±0.08 mm /yr in 1996 to 0.57 ±0.1 mm /yr in 2005. Several studies have projected up to 1.4 meters of sea level rise by 2100 when ice sheet contributions are included (e.g., Rahmstorf et al. 2007, Pfeffer et al. 2008). As sea level rises, storms will reach higher elevations leading to more extensive inundation (FitzGerald et al. 2008). The combination of sea level rise and storm surge will lead to a greater frequency of flood waters overtopping levees, breaking over seawalls, and breaching barriers. These threats may be magnified with climate change, as storms that lead to coastal storm surges are likely to become more intense and bring heavy precipitation and higher wind speeds (Williams et al. 2009). Recent studies suggest that hurricanes in the Altantic Ocean have increased in intensity over the past half century (Kunkel et al. 2008). 2,3_2 t If' p f' irrgoa is Coastal habitats, including tidal marshes, submerged aquatic vegetation, estuarine beaches, tidal flats, freshwater tidal forest systems, marsh and barrier islands, cliffs, and other coastal habitats are all at risk to losing area to inundation under sea level rise. Additionally, these communities face impacts from changes in tidal range, saltwater intrusion, erosion and increases in the frequency and duration of flood- ing. Shoreline habitats are complex and dynamic environments shaped by physical processes, sediment transport and deposition, geology, and changes in sea level (Gutierrez et al. 2009). Although it is widely recognized that sea level rise alters coastal landforms, predicting precisely how changes in the landscape will occur in response to sea level rise is a complex endeavor. Gesch et al. (2009) identify a number of impacts that coastal regions will face in response to sea level rise (Box 2 -3). Box 2 -3. Responses of a coastal regions to sea level rise ( Gesch et al. 2009) Land loss resulting from inundation of low lying lands Land loss due to erosion Barrier island migration, breaching and segmentation Wetland accretion and migration Wetland drowning (deterioration and conversion to open water) Expansion of estuaries Saltwater intrusion Increased frequency of storm flooding