PSMSL Annual Report for 1995

This report reviews briefly the work of the Permanent Service for Mean Sea Level (PSMSL) during 1995. This year, the PSMSL has continued its sea level databanking and data analysis activities. It has made major contributions to the development of the global sea level network. It has participated in important international conferences and working groups.

Data Holdings

In the period since the last Annual Report (i.e. since mid-December 1994), 1050 station-years of data were entered into the PSMSL database. This is somewhat less than the average yearly amount of around 1500. However, large updates from several countries await databanking, and we are confident that next year will see the average restored. The new sets of data are summarised in Appendix 1 and Figure 1. Major new contributions from Georgia, South Africa and China can be seen to be amongst those entered into the dataset. Anonymous FTP remains the main means by which data are distributed to scientists (via ftp node and directory /pub/psmsl), while CDROM and floppy disk products can also be provided depending on requirements.

GLOSS Status

The Global Sea Level Observing System (GLOSS) is an Intergovernmental Oceanographic Commission (IOC) project, one of the aims of which is to improve the quality and quantity of data supplied to the PSMSL. Each year, the PSMSL provides a summary of the status of GLOSS from its viewpoint. This summary is usually made in October so as not to bias the statistics because of the seasonal cycle of data receipts.

An `operational' station from a PSMSL viewpoint means that recent MSL monthly and annual values have been received at Bidston, have been checked as far as possible, and have been included in the databank. For each of the GLOSS stations we have used the year of the last data entered into the databank, if any, to place the station into one of four categories:

Category 1: `Operational' stations for which the latest data is 1991 or later;

Category 2: `Probably operational' stations for which the latest data is within the period 1981-1990;

Category 3: `Historical' stations for which the latest data is earlier than 1981;

Category 4: For which no PSMSL data exist.

Table 1 lists the number of stations which fall into each category, while Figure 2 indicates their spatial distribution. Also shown are the numbers in each category reported in the previous two years with the category definitions adjusted backwards appropriately.

                                        Table 1

                          Number of Stations in Each Category
              Category     93            94            95

              1            177           183           168
              2            33            35            59
              3            26            26            22
              4            72            64            59

              Total        308           308           308
It can be seen that, following the gradual improvements in the number of Category 1 stations for the last few years, this year saw a decline. This can be traced largely to the fact that for several countries with large numbers of GLOSS stations, the latest data available is from 1990. Consequently, those stations have been Category 1 for the last couple of years but have now fallen into Category 2. The two main countries in this set are Australia and Indonesia.

This reversal is so large as to hide definite progress in other areas. For example, several stations have been moved from Category 4 into 1, as can be seen from the number of Category 4's dropping to 59 from 64. This is partly a consequence of the on-going installation of new gauges as part of GLOSS, WOCE etc. The number of Category 3's has also been reduced. The overall result is that there is now a vast number of Category 2 stations (more than there have ever been, about a third of the number of Category 1 stations), which implies that there is a lot of data which is not finding its way into the databanks.

GLOSS Group of Experts Meeting 1995

The Fourth Session of the GLOSS Group of Experts met in Bordeaux during 31 January - 3 February 1995 to review the progress of the network, plan for the holding of GLOSS training courses and scientific meetings, and arrange for GLOSS-related products to be given maximum publicity. A report of that meeting is available from IOC as part of the `Reports of Meetings of Experts and Equivalent Bodies' series.

Dr.David Pugh, Chairman of the GLOSS Experts Group, decided during summer 1995 to retire from the Chairmanship after many years of service to GLOSS. Dr.Pugh and Prof.K.Wyrtki were the main originators of the IOC GLOSS programme in the mid-1980's. IOC has asked that Dr.Pugh remain a member of the Experts Group, and that Dr.Woodworth take on the role of Interim Chairman until the next Experts meeting in 1997.

IOC/GLOSS-IAPSO Southern Ocean Workshop and Bordomer'95

Prior to the GLOSS Experts gathering in Bordeaux, IOC and IAPSO held a joint meeting on the theme of `Sea Level Variability and Southern Ocean Dynamics'. Scientific presentations were made by a number of groups undertaking Southern Ocean sea level measurements, and a report of the meeting is available from IOC (IOC Workshop Report No.115).

Following the GLOSS Experts meeting, Drs.Woodworth and Pugh attended the Bordomer'95 conference in Bordeaux which was concerned with climate, sea level and coastal processes. Dr.Woodworth gave a presentation on the status of GLOSS, and on the combined use of altimeter and tide gauge data.

The GLOSS Bulletin

This year saw the production of the first two issues of the GLOSS Bulletin, a newsletter for sea level community on the World Wide Web (WWW) published by the PSMSL. The WWW address is:

In addition, the PSMSL has extended its provision of sets of WWW information on general sea level matters, which can be viewed via: (DEAD LINK)

European and UK Sea Level Projects and Working Groups

A new sea level study (`SELF-2') for the Mediterranean, in which Proudman Oceanographic Laboratory (POL) scientists are participating, has been approved for funding by the European Commission. The first SELF project made major advances in cataloguing and analysing Mediterranean sea level data, as well as in performing GPS and absolute gravity measurements in the region. Its continuation through SELF-2 is very encouraging. In addition, a proposal called `EuroGLOSS', for the effective densification of the GLOSS network in the European region, was written by Drs.Baker, Woodworth and Blewitt (Newcastle University) and was enthusiastically received both by European scientists and by the GLOSS Experts Group at their Bordeaux meeting. The EuroGLOSS proposal will be submitted for scientific publication, and will be put forward for possible European funding when appropriate.

In April 1995, Dr.Woodworth attended a meeting in Amsterdam, Netherlands concerned with a possible operational sea level network for the North Sea and a related programme of scientific research (NOSS). In May, Drs.Baker and Woodworth and other POL scientists gave presentations at a UK sea level meeting at Bidston sponsored by the Ministry of Agriculture, Fisheries and Food.

Related Altimetry Activities

Full participation has been maintained with the ERS-1 and TOPEX/POSEIDON (T/P) altimeter working groups. In May 1995, Dr.Woodworth attended a T/P Science Working Team meeting at the Jet Propulsion Laboratory, California. In late 1995, he also attended two meetings at ESA/ESTEC, Netherlands concerned with a proposal for the European Explorer Gravity and Ocean Circulation Experiment (GOCE) which may eventually provide a more precise model of the geoid for application to oceanographic studies.

IPCC 1995

The PSMSL has continued to participate in the sea level study group of the Intergovernmental Panel on Climate Change (IPCC). This included a meeting in Brighton, UK in March 1995 attended by Dr.Woodworth. Final versions of the IPCC report chapters are now nearing completion, with the sea level chapter being edited by Dr.R.A.Warrick, New Zealand.

IUGG Boulder 1995

Drs.Woodworth, Baker and Pugh attended the International Union of Geodesy and Geophysics (IUGG) conference in Boulder, USA in July 1995. Drs.Pugh and Woodworth presented a poster on the status of the PSMSL and GLOSS. One evening of the conference was set aside for a meeting of the Council of the Federation of Astronomical and Geophysical Data Analysis Service (FAGS), at which the activities of the PSMSL over the past four years were described and discussed.

Geodetic Fixing of Tide Gauge Benchmarks

A major development with regard to tide gauge benchmark fixing has been the establishment of the International GPS Service for Geodynamics (IGS). The present scenario for GPS measurements of benchmarks envisages the IGS providing the PSMSL with estimates of benchmark positions and velocities (i.e. vertical land movements). As the IGS will be linked to the International Earth Rotation Service (IERS) and thereby to FAGS, the interchange of data between services should be facilitated considerably. Discussions have taken place between Dr.Woodworth and Dr.Ruth Neilan (IGS) on how the first steps in this work might be made.

Tidal Science'96

A meeting entitled Tidal Science'96 will be held at the Royal Society, London in October 1996 organised by Dr.Woodworth and Dr.Richard Ray (Goddard Space Flight Center).


A number of technical and scientific reports have been published during 1995 (see below). These have included the use of GPS-buoys and coastal tide gauges for altimeter calibration studies, and analysis of data from the South Atlantic and Southern Ocean gauges.


Arrangements were made with the British Council and the National Institute of Oceanography, India for a technical specialist from the NIO (Mr.Antony Joseph) to receive three months tide gauge training at POL in the early part of 1995. That visit was very successful, and we hope that a similar arrangement can be made for a visit by a second specialist from India during 1996.

During 21 November - 1 December 1995, Dr.Woodworth attended an IOC GLOSS-GOOS sea level training course at the Survey of India, Dehra Dun, India and gave several lectures on sea level analysis, altimetry, oceanography and geodesy. Dr.P.Caldwell (University of Hawaii) and Prof.T.Murty (Flinders University) were also lecturers. This was a very successful training course which should stimulate considerably the sea level research activities in the Indian Ocean region.


In June 1995, the work of the PSMSL was described to approximately 2000 members of the public during POL Open Days. Separate presentations were made to local Members of Parliament. Several PSMSL-related scientists (Drs.Woodworth, Baker, Pugh) undertook student lecture courses during the year.

PSMSL Staffing

During 1995, Dr.M.Tsimplis left POL in order to take up another position elsewhere. Dr.Tsimplis has performed extensive PSMSL-related sea level analyses while at Bidston, as can be seen from the publication list for the year below. His post as part of the SELF/SELF-2 project will be filled by a new member of staff. Meanwhile, we hope to continue working with him on a number of sea level topics.

In addition, the Director of POL, Dr.B.S.McCartney, has provided resources for a further additional scientific staff position to be devoted to PSMSL and other sea level activities. This position will be advertised during early 1996.

Directing Board Arrangements

The IAPSO Commission on Mean Sea Level and Tides functions as the PSMSL Directing Board. Dr.C.Le Provost (France) was elected as President of the Commission at the IAPSO Conference in Hawaii in August 1995, replacing Dr.D.T.Pugh (UK) who has served as Commission President for many years. At the time writing, the membership of the new Commission is being finalised.

While the Commission will remain the body to which the PSMSL will report formally, discussions took place during 1995 on the means by which a more informal, but possibly more focused, PSMSL Advisory Group could also be established. Six scientists were approached to join the Group:

Dr.Ruth Neilan (Jet Propulsion Laboratory, USA) - in view of the importance of the overlap between PSMSL and IGS activities in future. Dr.Neilan is Director of the IGS Central Bureau;

Dr.Gary Mitchum (Univ.of South Florida, USA) - as a scientist with considerable experience of sea level databanking and analysis;

Prof.Bruce Douglas (Univ.of Maryland, USA) - as an analyst of the PSMSL dataset and with considerable expertise in satellite altimetry;

Dr.Richard Warrick (Univ.of Waikato, New Zealand) - as leader of the IPCC sea level studies and as a researcher into mechanisms of global sea level changes and their impacts;

Dr.David Pugh (Southampton Oceanography Centre, UK) - as a senior tidal and sea level scientist and as someone who knows PSMSL, GLOSS, IOC etc. matters extremely well;

and Dr.Georges Balmino (Bureau Gravimetrique International, France) - who has been asked by FAGS Council to be a member of the PSMSL Directing Board or Advisory Group and who is Director of another FAGS Service.

We are delighted that all six scientists agreed to be members of the Group, the first task of which will be to comment and advise on the PSMSL's work during 1995.

Visitors to the PSMSL

Visitors to the PSMSL during 1995 included Mr.A.Joseph (National Institute of Oceanography, India), Mr.A.Smith (Delft University of Technology, Netherlands), Prof.G.Brundrit (University of Cape Town, South Africa), Dr.P.Boudreau (LOICZ data systems manager, Netherlands Institute for Sea Research) and Drs.A.McKercher and D.Goring (New Zealand).


It can be seen that 1995 has been a busy year with a full programme of data collection and analysis and participation in international activities.

Particular thanks as usual go to Mrs. Elaine Spencer (PSMSL Secretary) and to members of staff of POL who contribute part of their time to PSMSL activities.

P.L.Woodworth (December 1995)

Relevant Reports

Ashkenazi, V., Lowe, D., Moore, T., Rae, J. and Woodworth, P.L. 1994. The use of GPS on buoys. pp.203-212 in, INSMAP94, Proceedings of the International Symposium on Marine Positioning, Hannover, Germany, September 19-23, 1994.

Baker, T.F., Woodworth, P.L. and Blewitt, G. 1995. A proposal for the definition of a strategic European network for sea level and coastal land level monitoring. POL and Newcastle University proposal submitted to the Intergovernmental Oceanographic Commission.

Lowe, D., Ashkenazi, V., Moore, D., Moore, T., Rae, J. and Woodworth, P.L. 1995. The use of GPS on buoys. Abstract of presentation at XXI General Assembly of the International Union of Geodesy and Geophysics, Boulder, Colorado, 2-14 July, 1995.

Meredith, M., Vassie, J.M., Woodworth, P.L., Hughes, C.W. and Heywood, K.J. 1995. The monitoring and forcing of the ACC at Drake Passage. pp.7-10 in, IOC/GLOSS-IAPSO Workshop on Sea Level Variability and Southern Ocean Dynamics, Bordeaux, France, 31 January 1995. Intergovernmental Oceanographic Commission Workshop Report No.115.

Murphy, C.M., Moore, P. and Woodworth, P.L. 1995. Short-arc calibration of the ERS-1 and TOPEX/POSEIDON altimeters utilising in-situ data. Journal of Geophysical Research. (In press).

Tsimplis, M.N. 1995. The response of sea level to atmospheric forcing in the Mediterranean. Journal of Coastal Research, 11(4), 1309-1321.

Tsimplis, M.N., Proctor, R. and Flather, R.A. 1995. A two-dimensional tidal model for the Mediterranean Sea. Journal of Geophysical Research, 100 (C8), 16223-16239.

Tsimplis, M.N. and Spencer, N.E. 1996. Collection and analysis of Monthly Mean Sea Level data in the Mediterranean and Black Sea. Journal of Coastal Research. (In press, to appear in volume 12(2)).

Tsimplis, M.N. 1995. Tides and sea level variability at the strait of Euripus. Submitted to Estuarine Coastal and Shelf Science.

Tsimplis, M.N. and Blackman, D. 1995. Extreme Sea Level Distribution and return periods in the Aegean and Ionian Seas. Submitted to Estuarine Coastal and Shelf Science.

Woodworth, P.L. and Vassie, J.M. 1994. The ACCLAIM programme in the South Atlantic and Southern Oceans. Afro-America GLOSS News, No.2 (October 1994), 2-3.

Woodworth, P.L., Windle, S.A. and Vassie, J.M. 1995. Departures from the local inverse barometer model at periods of five days in the Central South Atlantic. Journal of Geophysical Research, 100(C9), 18281-18290.

Woodworth, P.L. 1995. Monitoring and predicting long term sea level changes. (Abstract). Bordomer 95: Coastal Change conference 6-10 February, 1995, Bordeaux, France. In, Intergovernmental Oceanographic Commission Workshop Report No.105.

Woodworth, P.L. and Pugh, D.T. 1995. The Permanent Service for Mean Sea Level and the Global Sea Level Observing System. Abstract of presentation at XXI General Assembly of the International Union of Geodesy and Geophysics, Boulder, Colorado, 2-14 July, 1995. IUGG Book of Abstracts Week B, page B316.

Woodworth, P.L., Bell, C. and Hughes, C.W. 1995. Monitoring changes in global sea level and ocean transports with satellite altimetry and tide gauges. Abstract of presentation at XXI General Assembly of the International Union of Geodesy and Geophysics, Boulder, Colorado, 2-14 July, 1995. IUGG Book of Abstracts Week B, page B316.

Woodworth, P.L., Hughes, C.W., Vassie, J.M. and Meredith, M. 1995. Monitoring the variability of the ACC at Drake Passage with TOPEX/POSEIDON, and coastal and deep sea gauges, and comparisons to the FRAM model. pp.3-6 in, IOC/GLOSS-IAPSO Workshop on Sea Level Variability and Southern Ocean Dynamics, Bordeaux, France, 31 January 1995. Intergovernmental Oceanographic Commission Workshop Report No.115.

Zerbini, S., Plag, H.-P., Baker, T., Becker, M., Billiris, H., Burki, B., Kahle, H.-G., Marson, I., Pezzoli, L., Richter, B., Romagnoli, C., Sztobryn, M., Tomasi, P., Tsimplis, M., Veis, G. and Verrone, G. 1996. Sea Level in the Mediterranean: a first step towards separating crustal movements and absolute sea-level variations. Global and Planetary Change. (In press).

Appendix 1: Number of station-years entered into the databank for each country or coastline in the period mid-December 1994 to mid-December 1995 (1050 total).

 ICELAND                          2
 SPITSBERGEN                      13
 NORWAY                           23
 SWEDEN                           10
 POLAND                           10
 NETHERLANDS                      11
 BELGIUM                          12
 UNITED KINGDOM                   38
 IRELAND                          3
 CHANNEL ISLANDS                  1
 PORTUGAL                         8
 GIBRALTAR                        3
 MALTA                            5
 ITALY (ADRIATIC)                 1
 CROATIA                          7
 RUSSIA (BLACK SEA)               1
 GEORGIA                          103
 TURKEY                           4
 PORTUGAL (AZORES)                4
 PORTUGAL (MADEIRA)               6
 SPAIN (CANARY ISLANDS)           14
 CAPE VERDE ISLANDS               3
 SENEGAL                          8
 ASCENSION                        2
 GHANA                            4
 NIGERIA                          3
 ST. HELENA                       2
 NAMIBIA                          10
 SOUTH AFRICA                     49
 MOZAMBIQUE                       4
 SEYCHELLES                       1
 MAURITIUS                        8
 CHAGOS ARCHIPELAGO               2
 MALDIVES                         4
 TANZANIA                         1
 KENYA                            1
 SUDAN                            1
 MUSCAT & OMAN                    2
 INDIA                            16
 MALAYSIA                         12
 CHINA                            53
 HONG KONG                        22
 JAPAN (HOKKAIDO)                 19
 JAPAN (HONSHU-PACIFIC)           43
 JAPAN (SHIKOKU)                  8
 JAPAN (KYUSHU)                   25
 JAPAN (AMAMI GUNTO)              7
 SARAWAK                          2
 SABAH                            3
 PAPUA NEW GUINEA                 1
 NEW ZEALAND                      10
 GUAM                             2
 CAROLINE ISLANDS                 8
 PALAU ISLANDS                    1
 NAURU                            3
 MARSHALL ISLANDS                 5
 KIRIBATI                         1
 TUVALU                           1
 SOLOMON ISLANDS                  1
 NEW CALEDONIA                    1
 FIJI                             3
 AMERICAN SAMOA                   2
 PHOENIX ISLANDS                  1
 HAWAIIAN ISLANDS                 15
 LINE ISLANDS                     1
 PENRHYN ISLAND                   1
 ILES DE LA SOCIETE               2
 COOK ISLANDS                     1
 MARQUESAS                        1
 GAMBIER ISLAND                   1
 EASTER ISLAND                    2
 USA (ALASKA)                     22
 USA (PACIFIC COAST)              52
 MEXICO (PACIFIC)                 4
 CLIPPERTON ISLAND                4
 COSTA RICA (PACIFIC)             23
 PANAMA (PACIFIC)                 3
 ECUADOR                          5
 PERU                             4
 CHILE                            44
 ARGENTINA                        9
 BRAZIL                           15
 PANAMA (CARIBBEAN)               1
 BARBADOS                         2
 PUERTO RICO                      4
 VIRGIN ISLANDS                   4
 USA (GULF)                       43
 BAHAMAS                          2
 BERMUDA                          2
 USA (ATLANTIC)                   71
 ANTARCTICA                       13