Recent Relative Sea-level Change in Eastern North America

Eigenanalysis of tide-gauge records between 1920 and 1983 in eastern North America reveals highly variable spatial and temporal patterns of relative sea-level change. Auxiliary data from numerical modeling suggest that much of the long wavelength (thousands of km) spatial patterns of sea-level change are due to post-glacial isostatic adjustment of the land surface. Filtering the isostatic component from the rates of relative sea-level movement yields residual rates that fluctuate about a coastal mean of 1.0-1.5 mm/yr during this 64-year time interval. This mean rate is within the range of previous estimates of the mean rate of eustatic rise in sea level during the past century. Some residual fluctuations (wavelengths of tens to hundreds of km) correlate with tilts of the land surface revealed by geodetic leveling transects, and appear to be related to regional geology (i.e., basement structures and tectonic provinces in Florida, Georgia, the Carolinas, and the Chesapeake Bay area; fault reactivation in northern New England and the Maritime Provinces). These results suggest that tide-gauge data can be used to determine neo-tectonic movements along this coastline. Analysis of the temporal patterns of relative sea-level change reveals a gradual increase in the rate of rise centered at about 1934, which may be due to steric expansion of the ocean. Broad peaks in the spectrum of temporal sea-level fluctuations at 3-, 6-, and 20-year periodicities (significant at the 807% level) may be a reflection of oceanographic, atmospheric, and astronomical forcing. Thesis Supervisor: David G. Aubrey Title: Associate Scientist Woods Hole Oceanographic Institution