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Five Thousand Years of Sea-Level Change in Alaska
Reference
Jordan, J.W. and Mason, O.K.  1999.  A 5000 year record of intertidal peat stratigraphy and sea level change from northwest Alaska.  Quaternary International 60: 37-47.

What was done
The authors determined sea-level changes along a 140-km stretch of the southern Chukchi Sea in northwest Alaska from analyses of interbedded sequences of marsh peat and coastal flood deposits at 23 radiocarbon-dated sites on barrier islands and estuaries.

What was learned
It was determined that mean sea-level rose about 1.5 meters over the last 5,000 years.  The average rate-of-rise was 0.28 mm/yr.

What it means
Perhaps the greatest lesson to be learned from this study is that which comes from a comparison of its results with those of other recent studies of sea-level change during the late Holocene.  In our Journal Review Six Thousand Years of Sea Level Change in Eastern Maine, for example, we find a variety of sea-level rates-of-rise: 0.76 mm/yr, 0.43 mm/yr, 1.67 mm/yr, and 2.2 mm/yr, all of which are considerably larger than the Alaskan mean rate-of-rise.  Over the last century, The World's Longest Observational Sea-Level Record from Stockholm, Sweden also gives a larger result: a mean rate-of-rise of 1.0 mm/yr.  And it additionally suggests that since 800 A.D. there may have been some instances when sea-level actually fell, and by as much as 1.5 mm/yr.

Negative sea-level rates-of-change are also reported in Six Thousand Years of Sea Level Change in the Southern Hemisphere, where the data suggest that sea-level has fallen from approximately 6,000 to 600 years before present.  And in the study that spawned our Journal Review The Observational Sea Level Record of Mumbai, India: Is It Influenced More by Monsoon or Global Warming?, it is reported that sea-level rose at a rate of 2.2 mm/yr over the first half of the 20th century, but that it fell at a rate of about 1.2 mm/yr thereafter.

Could anything be more confusing?  Probably, but not much more.  Which leads us to think it would be wise to not place too much stock in any single study of sea-level change, and that it would be especially wise to not base energy policy on such data until a more consistent picture emerges, which may be quite a while yet in coming.


Reviewed 1 November 2000