"This is the first time that the rise has been adequately dated and it is also the first time it has been documented and verified in three locations, several hundred miles apart," explained Roland Gehrels, from the University of Plymouth in the UK. He and his colleagues studied records from Wells and Machiasport (northern Gulf of Maine) and Chezzetcook (Atlantic coast of Nova Scotia). Their findings jibed with those recorded in tide-gauge records.
"Tide-gauge records are instrumental records of sea-level change, measured directly with an instrument, usually from a harbor pier. Along the coast of Maine these records are available for the period since 1912," Gehrels said. "My records are geological reconstructions from salt marsh sediments. They go further back in time than the instrumental observations. The most recent part of my reconstruction, the part that covers the 20th century and thus overlaps with the instrumental record, gives the same values as the tide-gauge record. This is important because it is a check on the validity of the reconstruction. If they didn't match it would tell you something is wrong with the reconstruction!"
Gehrels will present these findings on Monday, November 5, at the Geological Society of America's annual meeting, A Geo-Odyssey, in Boston, Massachusetts.
Sea level rise in Nova Scotia (60 cm since 1750) and eastern Maine (50 cm since 1750) has been faster than in southwestern Maine (30 cm since 1750) because of gradual sinking of the coastline. This subsidence is caused by the lingering effects of the melting of the ice sheet that covered North America during the last ice age.
The 30-60 cm increase in sea-level rise along the coasts of Maine and Nova Scotia is unprecedented in the past millennium. Is this due to natural events or human interference? Or a combination of the two?
"There seems to be a two-stepped rise. First, sea level rose at the end of the 18th century as a result of natural climatic warming. In the 19th century, sea level didn't rise much at all. But at the beginning of the 20th century, sea level took off again, in tandem with global and hemispheric temperature rise," Gehrels explained.
"But sea level is rising faster now than during times when there was only 'natural' warming. This is a strong indication that current sea-level rise is not just the result of 'natural' warming but is, at least in part, caused by human-induced climate change."
Written by Kara LeBeau, GSA Staff Writer
CONTACT INFORMATION:
During the GSA Annual Meeting, November 4–8, contact Ann Cairns or Christa Stratton at the GSA Newsroom in the Hynes Convention Center, Boston, Massachusetts, for assistance and to arrange for interviews: (617) 954-3214.
The abstract for this presentation is available at: http://gsa.confex.com/gsa/2001AM/finalprogram/abstract_21164.htm.
Post-meeting contact information:
W. Roland Gehrels,
Department of Geographical Sciences
University of Plymouth
Plymouth N/A PL4 8AA United Kingdom
Phone: 44-1752-233079
E-mail: wrgehrels@plymouth.ac.uk
Ann Cairns
Director of Communications
Geological Society of America
Phone: 303-357-1056
Fax: 303-357-1074
acairns@geosociety.org
For more information about GSA visit our Web site at: http://www.geosociety.org