Commentaries on the Interpretation of Long Sea Level Records

By the staff and users of the Permanent Service for Mean Sea Level


The reports which can be accessed via this page have been written by a number of authors as a guide to users of the MSL data set who intend to use it to study trends and variability in a particular region. We call them 'commentaries'. The reports are NOT intended to be definitive, but simply to provide a personal overview of the data by way of introducing them. Please feel free to disagree with anything!

The first reason for the commentaries is simply to make clear the possibilities or limitations of the data set in a particular region. Sea level series recorded by tide gauges are subject to the sorts of issues found in any data recordings. The PSMSL already has documented many cautions in the data tables related to datum and instrument problems. Some additional examples may be given in a commentary. However, we do not intend a definitive examination of all records in these informal commentaries.

A second reason relates to the possible interpretations of the signals in the data sets. Tide gauge records of relative sea level show interesting signals over a very large range of frequencies, from semi-daily to centennial and longer. Variations about simple trends are due to a broad range of atmospheric and other forcings. This variability creates difficulties in estimating accurate long-term trends of sea level. However, these variations about trends are interesting in themselves. So one of our purposes for these commentaries on tide gauge records is to demonstrate their information content in as straightforward a way as we can so as to aid in their use for scientific purposes.

There is still much to be learned from sea level records, especially from the longer ones. This discussion of records is presented so that scientists and others who do not have a background in sea level analysis can rapidly appreciate the complexities of sea level data and use it more effectively in their research and teaching.

The Commentaries

Each commentary has been written by a different person and so will be different in style. However, we hope that you find them useful. Offers to write a commentary on the data from a country or region would be most welcome.

Commentaries so far available include:

[1] Remarks on the sea level records of the West Coast of North America (Bruce Douglas, 2007)

The idea for commentaries came from Bruce Douglas and this report was the first one received. It is a good model for others planning to write similar commentaries.

[2] Remarks on the sea level records of the North Indian Ocean (A.S. Unnikrishnan, 2007)

This report is a condensed version of the findings in a Global and Planetary Change paper by Unnikrishnan and Shankar.

[3] Sea level monitoring in Africa (P.L.Woodworth, A.Aman and T.Aarup, 2007)

This report started life as a commentary for this page but has been accepted for publication in the African Journal of Marine Science. The version accessible here is a 'post-print' of that paper. It indicates the present limitations of the African sea level data set and shows some of the longer records.

[4] We would point you to: Ragoonaden, S. 2006. Sea level activities and changes on the islands of the Western Indian Ocean. Western Indian Ocean Journal of Marine Science, 5(2), 179-194 for a description of the records from western Indian Ocean islands.

[5] A commentary on the use of tide gauge records for searching for fingerprints of Greenland and Antarctica melting etc. written by Bruce Douglas and published in the Journal of Coastal Research in 2008. This can be obtained by Clicking Here . This file contains a couple of corrections to the paper added to the pdf as notes.

Other commentaries are in preparation on the Mediterranean and other coastlines.