Investigating Sea Level Rise and Land Subsidence in the Coastal Cities of the New York Metropolitan Area: An InSAR Analysis Approach

This study investigates the contributions of coastal land subsidence to relative sea level rise (RSLR) in urban coastal regions of New York and New Jersey, addressing a gap in current research that often overlooks spatial variations in land motion. Utilizing Interferometric Synthetic Aperture Radar (InSAR), we mapped localized subsidence rates by processing over 150 Sentinel-1 images via the SBAS-InSAR technique. Furthermore, the study examines the spatial variations of vertical land motion (VLM), commonly known as land subsidence. The findings are validated with data collected from two Global Navigation Satellite System (GNSS) stations, one positioned in Brooklyn, New York, and another located in Sandy Hook Beach, New Jersey. This comparison reveals a significant difference in subsidence rates: Brooklyn shows a rate of 1.2 mm per year, while Sandy Hook Beach experiences a more substantial subsidence rate of 2.7 mm per year. These variations underscore the need for localized investigations when addressing the complex interplay between VLM and RSLR. A key aspect of our study is differentiating the contributions of VLM from sea-level rise trends. By subtracting the global mean sea-level rise rate of 3 mm per year from the local sea-level rise rate of 6 mm per year in Sandy Hook, we estimate the impact of land subsidence on RSLR. This analysis indicates that the coastal subsidence rate is approximately 3 mm per year, closely aligning with the observed local sea-level rise in Sandy Hook Beach, New Jersey. Our findings offer crucial insights into the role of subsidence in exacerbating coastal flood hazards, providing valuable information for coastal management and mitigation strategies.