S.E. Engelhart et al., Geology 37 (2009), Spatial variability of late Holocene and 20th century sea-level rise along the Atlantic coast of the United States

Geology (December 2009), Vol. 37, No. 12, pp. 1115-1118; DOI: 10.1130/G30360A.1

Spatial variability of late Holocene and 20th century sea-level rise along the Atlantic coast of the United States

Simon E. Engelhart^1,*, Benjamin P. Horton^1,*, Bruce C. Douglas², W. Richard Peltier³ and Torbjörn E. Törnqvist^4
1 Department of Earth and Environmental Science, University of Pennsylvania, 240 South 33^rd Street, Philadelphia, PA 19104, USA
² International Hurricane Research Center, Florida International University, 11200 SW 8^th Street, University Park, MARC 360, Miami, FL 33199, USA
³ Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A7, Canada
⁴ Department of Earth and Environmental Sciences and Tulane/Xavier Center for Bioenvironmental Research, Tulane University, 6823 St. Charles Avenue, New Orleans, LA 70118-5698, USA

Abstract

Accurate estimates of global sea-level rise in the pre-satellite era provide a context for 21^st century sea-level predictions, but the use of tide-gauge records is complicated by the contributions from changes in land level due to glacial isostatic adjustment (GIA). We have constructed a rigorous quality-controlled database of late Holocene sea-level indices from the U.S. Atlantic coast, exhibiting subsidence rates of <0.8 mm a^–1 in Maine, increasing to rates of 1.7 mm a^–1 in Delaware, and a return to rates <0.9 mm a^–1 in the Carolinas. This pattern can be attributed to ongoing GIA due to the demise of the Laurentide Ice Sheet. Our data allow us to define the geometry of the associated collapsing proglacial forebulge with a level of resolution unmatched by any other currently available method. The corresponding rates of relative sea-level rise serve as background rates on which future sea-level rise must be superimposed. We further employ the geological data to remove the GIA component from tide-gauge records to estimate a mean 20^th century sea-level rise rate for the U.S. Atlantic coast of 1.8 ± 0.2 mm a^–1, similar to the global average. However, we find a distinct spatial trend in the rate of 20^th century sea-level rise, increasing from Maine to South Carolina. This is the first evidence of this phenomenon from observational data alone. We suggest this may be related to the melting of the Greenland ice sheet and/or ocean steric effects.

*Correspondence e-mails: simoneng@sas.upenn.edu; bphorton@sas.upenn.edu


Link to abstract:  http://geology.geoscienceworld.org/cgi/content/abstract/37/12/1115