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About us

Since 1933, the Permanent Service for Mean Sea Level (PSMSL) has been responsible for the collection, publication, analysis and interpretation of sea level data from the global network of tide gauges. It is based in Liverpool at the Proudman Oceanographic Laboratory (POL) which is a component of the UK Natural Environment Research Council (NERC). The PSMSL is a member of the Federation of Astronomical and Geophysical Data Analysis Services (FAGS) established by the International Council for Science (ICSU). It is supported by FAGS, the Intergovernmental Oceanographic Commission (IOC) and NERC.

As of December 2006, the database of the PSMSL contains over 55000 station-years of monthly and annual mean values of sea level from almost 2000 tide gauge stations around the world received from almost 200 national authorities. On average, approximately 2000 station-years of data are entered into the database each year.

PSMSL stations throughout the world

Data for all stations are included in the PSMSL METRIC (or total) data set. The METRIC monthly and annual means for any one station-year are necessarily required to be measured to a common datum, although, at this stage, datum continuity between years is not essential. The year-to-year datum checks become essential, however, if the data are subsequently to be included in the PSMSL 'Revised Local Reference (RLR)' component of the data set.

The 'Revised Local Reference (RLR)' dataset of the PSMSL contains records for which time series analysis of sea level changes can be performed. Long records from this dataset have been the basis of all analyses of secular changes in global sea level during the last century. The geographical distribution of longer RLR records contains significant geographical bias towards the northern hemisphere, a situation which is being rectified by the establishment of the GLOSS global sea level network.

PSMSL stations with more than 40 years of records

For more information on the differences between 'Metric' and 'Revised Local Reference (RLR)' data values see the PSMSL help file.

For more background information on the PSMSL, see Woodworth, P.L. and Player, R. 2003. The Permanent Service for Mean Sea Level: an update to the 21st century. Journal of Coastal Research, 19, 287-295.

Reporting Arrangements

The PSMSL reports formally to the IAPSO Commission on Mean Sea Level and Tides (President Dr.P.L.Woodworth, UK). It is also served by an Advisory Group which at present consists of Dr.R.Neilan (JPL, USA), Dr.G.Mitchum (University of South Florida, USA), Prof.B.Douglas (University of Maryland, USA), Dr.D.Pugh (Liverpool University, UK), Dr.P.Knudsen (Danish National Space Center), Dr.J.Church (CSIRO, Australia), Dr.R.Bingley (Nottingham University, UK), Dr.T.Aarup (IOC, UNESCO) and Dr.J.Fierro (SHOA, Chile).

Suggestions for improvements in PSMSL activities may be sent directly to the PSMSL or via the IAPSO Commission or via any member of the Advisory Group.

Other Activities

The PSMSL attempts to stimulate the development of tide gauge networks with other countries at national, regional and global level. The most important component of this work is its planning, and part-management of, the GLOSS programme. It provides, through GLOSS and via other routes, advice and training to national sea level authorities and individual sea level scientists and technologists.

It organises major international meetings on the themes of sea level changes and tides e.g. the Linnean Society anniversary meeting in 1993, 'Tidal Science 96' at the Royal Society in London in 1996 and a 'Celebration of Sea Level Science' at the Royal Society in 2004.

It supplies software packages for tidal data analysis and quality control and helps with the provision of training information and manuals.

It maintains full participation with altimeter and space gravity working groups in view of the importance of those techniques to sea level research. The PSMSL Director is a Principal Investigator for the T/P, Jason, ERS and Envisat missions. Indeed, the future development of the global tide gauge network is closely linked to the symbiosis with precise altimetry and also with space gravity (GRACE and GOCE missions).

A wide range of publications are produced by the PSMSL. See these pages for web products. Printed publications include brochures, four manuals on tide gauge techniques, workshop reports (see under 'training materials' above) and reports to IOC and IUGG for large international conferences.

The file of technical publications relevant to the PSMSL and GLOSS are available, while review articles by the PSMSL Director and other authors provide a guide to the large number of scientific publications which have made use of the dataset.

Probably the most important recent scientific publications are those of the First (1990), Second (1995), Third (2001) and Fourth (2007) Scientific Assessments of Intergovernmental Panel on Climate Change (IPCC). The PSMSL Director has been a Lead Author for the sea level chapters in each of the IPCC studies. Major conclusions have been that global sea level has indeed risen by approximately 10-20 cm during the past century (see example plot here of some of the longest records from each region of the world: Takoradi, Ghana; Honolulu, Hawaii, USA; Sydney, Australia; San Francisco, USA; Brest, France) and may rise by amounts several times larger during the next century.

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