Subsidence along the Gulf and Atlantic coast of the United States exacerbates ocean inundation of the land produced by sea level rise

The increase in the rate of rise of global sea level, from 1.7 mm/yr in the 20th century to 3.1 mm/yr in the early 21st century, is caused mostly by increased ice loss from the Greenland and Antarctic ice sheets and from glaciers and by thermal expansion of the oceans in response to the warming of the Earth. Moreover, land subsidence in many places along the coast increases the rate of rise of relative sea level and exacerbates sea inundation of the land [Shirzaei and Burgmann 2018]. In this study, we analyze GPS measurements of the displacement of solid Earth's surface from 2006 to the Present along the coast and in the interior of the United States. We furthermore determine the area of land that will be inundated by ocean accounting for global sea level rise and for coastal subsidence. We find an 800 km stretch of the Texas and Louisiana coast to be subsiding at 2 to 5 mm/yr (See illustration). The rate of relative sea level rise along this belt along the coast of the Gulf of Mexico is 5 to 8 mm/yr, 100 to 166 per cent faster than the rate of rise of global sea level. Florida is subsiding hardly at all, between 0 and 1 mm/yr. The New Jersey and northern Virginia coast is subsiding at 2 mm/yr, and the Chesapeake Bay coast is subsiding at 1 to 2 mm/yr (Fig. 2). This moderately fast subsidence increases relative sea level there by 33 to 66 percent to 4 to 5 mm/yr. New England has nearly zero vertical motion. In the eastern and central United States, the peripheral bulge of the former Laurentide ice sheet is predicted by ICE-6G_D (VM5a) [Peltier et al. 2015, 2018; Argus et al. 2014] to be collapsing at 2 mm/yr, slightly exceeding that observed by GPS in the reference frame defined by Earth's (CM) center of mass in ITRF2015. The Fifth Assessment (AR5) of the Intergovernmental Panel on Climate Change (IPCC) projects global sea level to rise 0.2 to 2 m by 2100, with the range of values reflecting different Representative Concentration Pathways (RCP's). Herein we will adapt such projections, satellite altimetry measurements of sea level rise in the Atlantic Ocean, and our determination of vertical motion along the Gulf and East coast of the U.S. to determine the area of land along the U.S. Gulf and Atlantic coast that will be inundated by ocean by 2100.