Subsidence along the Atlantic Coast of North America: Insights from GPS and Late Holocene Relative Sea Level Data

• Main Authors: Karegar, Makan A., Dixon, Timothy H., Engelhart, Simon E.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Digital Commons @ University of South Florida 2016
• Subjects: Holocene relative sea level; GPS; glacial isostatic adjustment; Atlantic Coast of North America; groundwater depletion; Earth Sciences; Ice Sheet
• Online Access: https://digitalcommons.usf.edu/geo_facpub/1527; https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=2497&context=geo_facpub

The Atlantic Coast of North America is increasingly affected by flooding associated with tropical and extratropical storms, exacerbated by the combined effects of accelerated sea‐level rise and land subsidence. The region includes the collapsing forebulge of the Laurentide Ice Sheet. High‐quality records of late Holocene relative sea‐level (RSL) rise are now available, allowing separation of long‐term glacial isostatic adjustment‐induced displacement from modern vertical displacement measured by GPS. We compare geological records of late Holocene RSL to present‐day vertical rates from GPS. For many coastal areas there is no significant difference between these independent data. Exceptions occur in areas of recent excessive groundwater extraction, between Virginia (38°N) and South Carolina (32.5°N). The present‐day subsidence rates in these areas are approximately double the long‐term geologic rates, which has important implications for flood mitigation. Tide gauge records, therefore, should be used with caution for studying sea‐level rise in this region.