Investigating Vertical Land Motions in the Chesapeake Bay of Eastern North America with GPS and InSAR

The Chesapeake Bay of eastern North America is experiencing high rates of spatially variable relative sea-level rise, in part due to land subsidence, that pose significant coastal hazards. Previous measurements of vertical land motion (VLM) in the area from Global Positioning System (GPS) and InSAR give conflicting results at small scales, but find regional scale rates of land subsidence on the order of ~1-4 mm/yr. In this work, we revise VLM estimates using continuous GPS and InSAR that span July 2016 - December 2020. We use GAMIT-GLOBK for 3D velocities and HECTOR to model uncertainties that include white noise, flicker noise, and time-correlated noise. After applying the Robust Network Imaging algorithm of Kreemer et al. (2020) to the continuous GPS data, we find maximum subsidence of -3.4 +- 0.5 mm/yr in the Virginia Beach area. A 3D inversion of ascending Sentinel-1 data with our GPS velocities reveals comparable estimates of land subsidence in the Chesapeake Bay. Estimates of VLM from glacial isostatic adjustment based on the ICE7G model (about -0.5 to -1.2 mm/yr) are removed from the absolute VLM rates. Residual land subsidence rates continue to be relatively higher at approximately -3 mm/yr in the Virginia Beach area. These results will be compared with new vertical land motion estimates from an ongoing 5-year GPS campaign that began in 2019 and an independent estimate of VLM based on continuous GPS using the MIDAS approach. We will also present the ongoing GPS campaign, which will ultimately be incorporated into our VLM map of the area. Results from this study will be valuable to stakeholders and decision makers in the Chesapeake Bay.