PSMSL Annual Report for 1996

This report reviews briefly the work of the Permanent Service for Mean Sea Level (PSMSL) during 1996. This year the PSMSL has continued its sea level databanking and data analysis activities and has undertaken a major review of the possible development of the Global Sea Level Observing System (GLOSS). It has taken part in international scientific working groups and has organised an important meeting entitled `Tidal Science 1996'.

Data Holdings

In the period since the last Annual Report (i.e. since mid-December 1995), over 2500 station- years of data were entered into the PSMSL database. This is two and half times more than the number entered in the previous year. Although a large part of this data entry consisted in a major update of Australian data, other large contributions were received from, for example, Greece, Papua New Guinea, Malaysia, Chile and Canada. The new sets of data are summarised in Appendix 1 and Figure 1. Anonymous FTP remains the main means by which data are distributed to scientists (via ftp node and directory /pub/psmsl), while CD-ROM 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 1992 or later;

Category 2: `Probably operational' stations for which the latest data is within the period 1982-1991;

Category 3: `Historical' stations for which the latest data is earlier than 1982;

Category 4: For which no PSMSL data exist.

The spatial distribution of stations in each category as of October 1996 is shown in Figure 2, while Figure 3 indicates the numbers in each category reported in previous years with the category definitions adjusted backwards appropriately. It can be seen that the number of Category 1 stations has never been higher.

Other GLOSS Developments

In July 1996, the British Oceanographic Data Centre (BODC) and the PSMSL produced a CD-ROM version of the GLOSS Station Handbook product for the `Second Conference of Parties of the UN Framework Convention on Climate Change' in Geneva, Switzerland. This CD-ROM contains full details of each gauge in GLOSS including site maps; scanned images of IOC training manuals; and the various PSMSL data and information files. Copies of the CD-ROM have been distributed widely.

In preparation for the fifth meeting of the GLOSS Group of Experts at the Jet Propulsion Laboratory, California in March 1997, the PSMSL Director, who is also Chairman of the GLOSS Group, has prepared a draft version of a new Implementation Plan for GLOSS. It is intended that this document be as widely distributed and discussed as possible, for eventual approval by the XIX'th Session of the IOC Assembly in July 1997.

The year saw the production of the third and fourth issues of the GLOSS Bulletin, a newsletter for the sea level community on the World Wide Web (WWW) published by the PSMSL (

European and UK Sea Level Projects

A European Commission funded sea level study (`SELF-2') for the Mediterranean, in which Proudman Oceanographic Laboratory (POL) scientists are participating, has continued into its second year, with concentration at POL on MSL changes, storm surge modelling and tidal loading. In addition, a proposal called `EuroGLOSS', for the effective densification of the GLOSS network in the European region, was written by scientists from POL/PSMSL, Newcastle University and IGN, France, has been accepted for publication in the Journal of Marine Systems.

Consultations have taken place with colleagues in Greece with regard to collaborative upgrading of some of the Greek tide gauge sites.

During the year, POL and the PSMSL contributed strongly to a proposal for a large UK funded `thematic' programme of research into sea level changes. This proposal was highly graded by the UK Natural Environment Research Council, although decisions on ultimate funding will be delayed until 1997.

Visits to GLOSS Gauge Sites

During the year, Dr.Woodworth paid visits to gauges at Ascension Island and Cananeia, Brazil. The latter visit took place in December during a Symposium on Oceanography at the University of Sao Paulo which was held to mark the 50'th anniversary of the Instituto Oceanografico.

IPCC 1995

The Second Scientific Assessment of the Intergovernmental Panel on Climate Change (IPCC), in which the PSMSL contributed to Chapter 7 (Sea Level Changes) was published during the year.

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.

In March 1997, a meeting on tide gauge benchmark fixing will be held at the Jet Propulsion Laboratory, prior to the GLOSS Experts meeting. This meeting will be organised jointly by the IGS Central Bureau (Dr.Ruth Neilan), the PSMSL and IOC/GLOSS.

Altimetry and Gravity Field Activities

Full participation has been maintained with the ERS-1/2 and TOPEX/POSEIDON (T/P) altimeter working groups. In July, Dr.Woodworth organised a session on altimetry and ocean circulation at the COSPAR conference in Birmingham, UK. In October, he attended a T/P Science Working Team meeting at the Southampton Oceanography Centre, UK. The year also saw the completion of a UK Defence Research Agency funded project at POL for mapping variations in global sea surface topography using T/P data. It is intended that this work will continue as part of ongoing PSMSL/POL research.

In May, Dr.Woodworth attended a meeting in Granada, Spain organised by the European Space Agency to discuss possible `Explorer' Missions by the Agency. Subsequently, the proposal for a `Gravity Field and Steady State Ocean Circulation Experiment' (GOCE), of which he had a been a co-author, was accepted by the agency, with the proposed mission now proceeding to Phase A study. The provision of a more precise model of the Earth's gravity field and geoid is of great importance to a range of oceanographic and geophysical studies.

Tidal Science 1996

A successful meeting entitled Tidal Science 1996 was held at the Royal Society of London during 21-22 October, organised by Dr.Woodworth and Dr.Richard Ray (Goddard Space Flight Center). This meeting was held on the 70'th birthday of Dr.D.E.Cartwright, FRS and it is intended that a special issue of Progress in Oceanography will be devoted to papers arising from the meeting.


During the first part of the year, the British Council funded an Indian scientist (Mr.C.Biswas of the Survey of India) to visit and study tide gauge techniques at POL. This successful visit followed that of another Indian scientist (Mr.Antony Joseph) from the National Institute of Oceanography the previous year. This activity reflects the increased Indian interest in sea level matters in general, and GLOSS in particular.

In November, Dr.David Pugh represented the PSMSL at an IOC funded training course on sea level and tidal analysis in Buenos Aires, Argentina. Arrangements have been made for IOC funding of a training course on sea level to be held at POL during the summer of 1997, probably with emphasis on the needs of African and Mediterranean countries. This course will be in a similar style (formal lectures and `hands-on training') to that of a course held in Dehra Dun, India in 1995.

Media, `Outreach' and Publications

Radio interviews describing the sea level work of POL and the PSMSL were given during the year to BBC Radio 4 and Radio Merseyside. During December, an extended series of Radio 2 broadcasts was made by POL staff while on a science and resupply cruise across the Drake Passage to Antarctica, which included refurbishment of tide gauges in the area.

An overview of the PSMSL's activities has been provided to the FAGS Secretary for inclusion in an updated publication describing the work of the FAGS Services.

Seminars on sea level studies were given during the year at Liverpool and Southampton Universities and West Cheshire College.

A number of scientific and technical reports have been published during 1996 (see below).

PSMSL Staffing

The Director of POL, Dr.B.S.McCartney, has provided resources for an additional scientific staff position to be devoted to PSMSL and other sea level activities. A scientist from the University of Plymouth will take up this post in January 1997.

Directing Board and Advisory Group

The IAPSO Commission on Mean Sea Level and Tides functions as the formal PSMSL Directing Board. Dr.C.Le Provost (France) is its President. The year 1996 was the first in which an additional PSMSL Advisory Group has been established to provide more informal, but possibly more focused, advice. Six highly-regarded scientists were approached to join the Group: Dr.Ruth Neilan (Jet Propulsion Laboratory, USA), Dr.Gary Mitchum (Univ.of South Florida, USA), Prof.Bruce Douglas (Univ.of Maryland, USA), Dr.Richard Warrick (Univ.of Waikato, New Zealand), Dr.David Pugh (Southampton Oceanography Centre, UK) and Dr.Georges Balmino (Bureau Gravimetrique International, France). Dr.Balmino had already been asked by FAGS Council to be a member of the PSMSL Directing Board or Advisory Group, and is Director of another FAGS Service.

Most of the six commented very usefully on the PSMSL Annual Report for 1995 and their advice will be asked for, and acted upon, with regard to this year's Report.

Visitors to the PSMSL

Visitors to the PSMSL during 1996 included Mr.C.Biswas (Survey of India), Mesquita and Mr.C.Franca (University of Sao Paulo, South Africa), Mr.C.Quartley (Valeport Ltd., UK), Dr.D.Pugh (Southampton Oceanography Centre, UK), Mr.D.Warrilow (Department of the Environment, UK), Dr.R.Ray (Goddard Space Flight Center, USA), Mr.R.Summerson (National Resource Information Centre, Australia), Prof.K.Lambeck (Australian National University, Canberra), Dr.G.Kivman (Shirshov Institute, St.Petersburg, Russia), Prof.A.Wroblewski (Polish Academy of Sciences), Dr.O.B.Andersen (KMS, Copenhagen, Denmark), Dr.A.M.Duda (World Bank) and Prof.Xie Shi Zhong, Prof.Li De-Yang and Mrs.Liu Jing-Mei (Wuhan Transportation University, China).


It can be seen that 1996 has been a fruitful year with regard to data acquisition, with the promise of increased levels of staff support in 1997, and also a busy year with regard to participation in international scientific gatherings.

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

P.L.Woodworth (December 1996)

Some Recent Relevant Reports

Ashkenazi, V., Moore, T., Lowe, D., Moore, D., Woodworth, P.L. and Rae, J. 1996. Offshore sea measurement using GPS. Civil Engineering Surveyor, GIS/GPS Supplement, Autumn 1996, 21-23.

Balmino, G., Sabadini, R., Tscherning, C. and Woodworth, P.L. 1996. Gravity Field and Steady-State Ocean Circulation Mission. Reports for assessment: the nine candidate Earth Explorer Missions. European Space Agency Report SP-1196(1). 77pp.

Baker, T.F., Woodworth, P.L., Blewitt, G. Boucher, C. and Woppelmann, G. 1996. A European network for sea level and coastal land level monitoring. Journal of Marine Systems (in press).

Bell, C., Vassie, J.M. and Woodworth, P.L. 1996. The Tidal Analysis Software Kit (TASK Package). (PSMSL/POL floppy disk package for tidal analysis and accompanying manual). Dated 1 January 1996.

Meredith, M.P., Vassie, J.M., Heywood, K.J., Woodworth, P.L. and Hughes, C.W. 1996. The temporal variability of the transport through Drake Passage. Ocean Sciences Meeting, 11-15 February 1996, San Diego, California. EOS, Transactions, American Geophysical Union, 76, No.3, p87.(16 January 1996).

Murphy, C.M., Moore, P. and Woodworth, P.L. 1996. Short-arc calibration of the ERS-1 and TOPEX/POSEIDON altimeters utilising in-situ data. Journal of Geophysical Research, 101(C6), 14191-14200.

Rickards, L.J., Cramer, R.N., Tabor, A.R., Spencer, N.E., Woodworth, P.L. and Jones, M.T. 1996. The GLOSS Handbook CD-ROM (July 1996). A CD-ROM product containing the PSMSL dataset from the British Oceanographic Data Centre, Proudman Oceanographic Laboratory, Birkenhead, UK.

Shum, C.K., Woodworth, P.L., Andersen, O.B., Egbert, G., Francis, O., King, C., Klosko, S., Le Provost, C., Li, X., Molines, J-M., Parke, M., Ray, R., Schlax, M., Stammer, D., Tierney, C., Vincent, P. and Wunsch, C. 1996. Accuracy assessment of recent ocean tide models. Submitted to the Journal of Geophysical Research.

Warrick, R.A., Le Provost, C., Meier, M.F., Oerlemans, J. and Woodworth, P.L. 1995. Lead authors of Chapter 7 (Changes in sea level) of Climate Change 1995. The science of climate change. Contribution of working group I to the second assessment report of the Intergovernmental Panel on Climate Change, eds. J.T.Houghton, L.G.Meira Filho, B.A.Callander, N.Harris, A.Kattenberg and K.Maskell. Cambridge: Cambridge University Press. 572pp.

Woodworth, P.L. 1995. One of 19 Contributors to Chapter 9 (Coastal zones and small islands. Lead author L.Bijlsma) of Climate Change 1995. Impacts, adaptations and mitigation of climate change: scientific-technical analysis. Contribution of working group II to the second assessment report of the Intergovernmental Panel on Climate Change, eds. R.T.Watson, M.C.Zinyowera and R.H.Moss. Cambridge: Cambridge University Press. 879pp.

Woodworth, P.L., Vassie, J.M., Spencer, R. and Smith, D.E. 1996. Precise datum control for pressure tide gauges. Marine Geodesy, 19(1), 1-20.

Woodworth, P.L., Vassie, J.M., Hughes, C.W. and Meredith, M.P. 1996. A test of the ability of TOPEX/POSEIDON to monitor flows through the Drake Passage. Journal of Geophysical Research, 101(C5), 11935-11947.

Woodworth, P.L., Shum, C.K., Le Provost, C. and Ray, R.D. 1996. Significant Improvement in Ocean Tide Models. International WOCE Newsletter, No.24, 36-38.

Appendix 1: Number of station-years entered into the databank for each country or coastline in the period mid-December 1995 to mid-December 1996 (2514 total).

 ICELAND                          3
 SPITSBERGEN                      3
 NORWAY                           22
 SWEDEN                           10
 NETHERLANDS                      14
 UNITED KINGDOM                   40
 IRELAND                          1
 CHANNEL ISLANDS                  1
 ITALY (ADRIATIC)                 1
 SLOVENIA                         1
 CROATIA                          13
 GREECE                           100
 TURKEY                           8
 PORTUGAL (AZORES)                1
 SENEGAL                          1
 ASCENSION                        2
 NIGERIA                          3
 ST. HELENA                       2
 MOZAMBIQUE                       13
 COMOROS                          4
 MADAGASCAR                       3
 SEYCHELLES                       3
 MAURITIUS                        4
 CHAGOS ARCHIPELAGO               1
 MALDIVES                         9
 TANZANIA                         2
 KENYA                            3
 GULF                             17
 MUSCAT & OMAN                    3
 INDIA                            3
 BANGLADESH                       23
 MALAYSIA                         36
 SINGAPORE                        15
 INDONESIA                        2
 CHRISTMAS ISLAND                 6
 VIETNAM                          4
 HONG KONG                        8
 TAIWAN (FORMOSA)                 4
 JAPAN (HOKKAIDO)                 14
 JAPAN (HONSHU-PACIFIC)           35
 JAPAN (SHIKOKU)                  8
 JAPAN (KYUSHU)                   18
 JAPAN (AMAMI GUNTO)              5
 SARAWAK                          6
 SABAH                            9
 PAPUA NEW GUINEA                 101
 AUSTRALIA                        1371
 GUAM                             1
 PALAU ISLANDS                    2
 NAURU                            1
 MARSHALL ISLANDS                 6
 KIRIBATI                         3
 TUVALU                           3
 SOLOMON ISLANDS                  2
 NEW CALEDONIA                    7
 VANUATU                          6
 FIJI                             5
 TONGA                            5
 AMERICAN SAMOA                   1
 HAWAIIAN ISLANDS                 11
 LINE ISLANDS                     4
 PENRHYN ISLAND                   2
 ILES DE LA SOCIETE               4
 COOK ISLANDS                     4
 MARQUESAS                        2
 GAMBIER ISLAND                   2
 EASTER ISLAND                    2
 USA (ALASKA)                     13
 CANADA (PACIFIC COAST)           60
 USA (PACIFIC COAST)              20
 MEXICO (PACIFIC)                 21
 EL SALVADOR                      10
 COSTA RICA (PACIFIC)             12
 PANAMA (PACIFIC)                 7
 COLOMBIA (PACIFIC)               4
 ECUADOR                          6
 PERU                             4
 CHILE                            43
 URUGUAY                          22
 BRAZIL                           3
 PANAMA (CARIBBEAN)               1
 GUADELOUPE                       2
 MEXICO (GULF)                    4
 CUBA                             7
 PUERTO RICO                      2
 VIRGIN ISLANDS                   2
 USA (GULF)                       20
 BAHAMAS                          1
 BERMUDA                          1
 USA (ATLANTIC)                   39
 ANTARCTICA                       18