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Six Thousand Years of Sea Level Change in Eastern Maine
Reference
Gehrels, W.R.  1999.  Middle and late Holocene sea-level changes in eastern Maine reconstructed from foraminiferal saltmarsh stratigraphy and AMS 14C dates on basal peat.  Quaternary Research 52: 350-359.

What was done
The author employed two different methods to reconstruct a sea-level history for Machiasport, Maine, spanning the past 6,000 years.  The first method established the mean trend over the period by dating the base of the local saltmarsh peat that overlies a Pleistocene substrate.  The second method relied upon "detailed analyses of the foraminiferal stratigraphy of two saltmarsh peat cores to quantify fluctuations superimposed on the long-term trend."

What was learned
For the first 4,500 years of the record, the mean rate of sea-level rise was determined to be 0.75 mm/yr; while for the final 1,500 years, it averaged only 0.43 mm/yr.  Over the last 300 years, however, the mean rate-of-rise rose to a value of 1.67 mm/yr; and since 1930 it has averaged 2.2 mm/yr, as measured by a local tide gauge.

What it means
Much like what we are being told relative to surface air temperature trends, the author notes that the high rate-of-rise of the sea-level since 1930 "is unprecedented in the past two millennia."  However, he tempers the implications of this statement with the acknowledgement that "as the onset of rapid sea-level rise occurred before industrial times..., at least some of this rise is probably part of a natural oscillation."  Or as he puts it another way, "the rapid rise has been ongoing since before industrial times and must therefore contain a natural component."

Two thoughts come to mind with respect to these observations.  First, the 1930-present tide gauge readings may be erroneously yielding a rate of sea-level rise that is too great, as is implied by the work described in our Journal Review The World's Longest Observational Sea-Level Record.  Second, since the "unprecedented" rate of sea-level rise began "before industrial times," most if not all of it must be of natural or non-anthropogenic origin.  The challenge we face, therefore, is to determine the nature of that natural component and the cause of its natural oscillation.

Sorry, climate alarmists.  This result does not confirm your contentions about man-made global warming.


Reviewed 1 November 2000