PSMSL Annual Report for 1999

1. Introduction

This report reviews briefly the work of the Permanent Service for Mean Sea Level (PSMSL) during 1999. This year the PSMSL has continued with its primary task of assembly of the global data set of sea level change information, has taken the major role in the development of the Global Sea Level Observing System (GLOSS), and has contributed to important international conferences and working groups concerned with sea level and climate change.

2. PSMSL Data Receipts for 1999

In the period since the last Annual Report (i.e. since mid-December 1999), over 900 station-years of data were entered into the PSMSL database. This is slightly less than the amount entered in a normal year, primarily owing to a number of disruptions caused by changes to staff in the Centre for Coastal and Marine Sciences (CCMS) of the which the Proudman Oceanographic Laboratory (POL) is a component. It is anticipated that entries will be fully back to normal during 2000.

Appendix 1 lists countries from which sea level data were obtained, while Figure 1 shows their locations. A notable addition to the data set can be seen from Vietnam. Of particular interest (although perhaps not of special scientific importance) is a near complete sea level record, commencing in the 1870s, that has been assembled for the historic city of Venice with the help of Italian colleagues.

3. GLOSS Activities

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. GLOSS can be considered as one of the first components of the Global Ocean Observing System (GOOS).

3.1 GLOSS Status from a PSMSL Viewpoint (October 1999)

For the last few years, usually coinciding with a GLOSS GE meeting, the PSMSL has provided a summary of the status of GLOSS from its viewpoint. This summary has usually been 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 Mean Sea Level (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 1995 or later;
Category 2: 'Probably operational' stations for which the latest data is within the period 1985-1994;
Category 3: 'Historical' stations for which the latest data is earlier than 1985;
Category 4: For which no PSMSL data exist.

Figure 2 lists the numbers of stations which fall into each category for all stations, while Figure 3 shows their locations. Also shown in Figure 2 are the numbers in each category reported previously with the category definitions adjusted backwards one, two, three etc. years appropriately. (Before 1993 we used the 'GLOSS90' definition of GLOSS containing 306 stations total; 1993 onwards we used 'GLOSS93' containing 308 stations; 1997 onwards we used 'GLOSS97' with 287 stations). Overall, the statistics for 1999 are similar to those for 1998 indicating ongoing work is required to develop the network even further.

In brief, GLOSS can be considered approximately two-thirds operational, if one uses data receipts by the PSMSL as a guide to operational status. However, the overall status is somewhat better than that. At some gauge locations (e.g. Tristan da Cunha and some Antarctic sites), the gauges take the form of simple pressure transducers which provide useful information for oceanography (e.g. for the World Ocean Circulation Experiment, WOCE) but which do not supply MSL data, as conventionally defined, which can subsequently be submitted to the PSMSL. This situation is understandable and tolerable if there are good environmental or technical reasons for such a choice of technology. At other locations, while a perfectly good gauge might exist and be providing data of some kind, the expertise or facilities or manpower do not exist in order to process those data routinely and deliver them to the international community. This situation is not an acceptable one, as it clearly requires some kind of investment in hardware, software or training. The job of IOC/GLOSS and of the PSMSL is to remedy such situations as far as possible and to improve GLOSS status as far as possible.

3.2 GLOSS Training Courses

The PSMSL has taken the lead in the organisation of GLOSS training courses in almost every year since 1983. The most recent were at Dehra Dun, India (1995), Buenos Aires, Argentina (1996), POL, UK (1997) and Cape Town, South Africa (1998). A further course took place at the University of Sao Paulo, Brazil in September 1999 organised by Prof. Afranio de Mesquita and with Drs. Baker and Vassie from POL as guest lecturers. As with previous courses, the Sao Paulo agenda concerned itself with background sea level science (climate change, oceanography), the need for related geodetic measurements, and 'hands on training sessions' (HOTS). In November, Dr. David Pugh represented the PSMSL at a climate conference in Saudi Arabia and obtained local national and regional support for a further IOC course concentrating on GLOSS and GOOS (the Global Ocean Observing System) in May 2000 for students from the Middle East.

3.3 GLOSS Newsletters

The PSMSL publishes a newsletter for the GLOSS community called the GLOSS Bulletin of which issue 7 published in 1999 can be found on the web at:

An updated two page brochure advertising GLOSS in English was produced by the PSMSL in 1998 since when a new version in Portuguese has been provided to the PSMSL by Dr. E. Marone from Brazil.

3.4 GLOSS Handbook

Sea level researchers will be familiar with the GLOSS Handbook product available on the web and edited by Dr. Lesley Rickards of the British Oceanographic Data Centre (BODC). The Handbook was updated and extended during 1999 by means of rounds of correspondence with GLOSS Contacts and a survey conducted at the GE6 meeting in May (see below). Further major updates are planned in 2000 with the emphasis on the provision of metadata including maps and photographs.

3.5 Sixth Meeting of the GLOSS Group of Experts

The sixth meeting of the GLOSS Group of Experts (GE6) took place in Toulouse, France in May with the local organisation provided kindly by Dr. C. Le Provost. It was preceded by a workshop on 'Ocean Circulation Science derived from the Atlantic, Indian and Arctic Sea Level Networks' organised by Dr. Gary Mitchum and a workshop on 'GPS at Tide Gauge Benchmarks for Long Term Sea Level Change Studies and for Altimeter Calibration' organised by Prof. Mike Bevis. The many conclusions and recommendations from these meetings can be found on the web at: in Wordperfect format or in ascii.

One of the most important outcomes of GE6 was the decision to establish a Scientific Steering Group (SSG), initially as a sub-group of the Group of Experts but eventually as a joint group with other GLOSS-related programmes (e.g. OOPC, CLIVAR-UOP, IAPSO CMSLT). Dr. Gary Mitchum has since agreed to chair the SSG, which will contain representatives of each of the main areas of research in GLOSS, and which will be able to advise the Group of Experts as appropriate as scientific priorities develop in future.

4. 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). In March 1997, a meeting on tide gauge benchmark fixing was held at the Jet Propulsion Laboratory, prior to the fifth meeting of the GLOSS Experts. This meeting was organised jointly by the IGS Central Bureau (Director, Dr. Ruth Neilan), the PSMSL and IOC/GLOSS and resulted in an excellent workshop report on the use of GPS at gauge sites for measuring long term changes in vertical land movements and for altimeter calibration. In May 1999, a follow-up meeting was held at Toulouse, France alongside GE6 (see above) with plans for a Manual on 'How to Operate GPS at Gauges' put in place for probable publication in 2000.

Recently, a survey has been conducted on behalf of the PSMSL, EUREF and other organisations on the availability of permanent GPS stations near to tide gauges. The survey was undertaken by Dr. Guy Woppelmann of SHOM, France and first results can be found via:

This web page also contains a mechanism by which the community should be able to keep the information up-to-date as a 'living document'.

5. Related Scientific Meetings and Study Groups

5.1 Intergovernmental Panel on Climate Change ( IPCC) Third Assessment Report

The Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) has continued under development in 1999 with Chapter 11 on sea level changes led by Dr. J. Church (Australia) and Dr. J. Gregory (UK) and with Dr. Woodworth as a Lead Author. The next chapter meeting is planned for New Zealand in February 2000 with final publication of the TAR in January 2001.

5.2 Altimetry and Gravity Field Activities

Participation has continued in European and US altimeter working groups during the period. Dr. Woodworth is a Principal Investigator for the TOPEX/POSEIDON and JASON-1 missions and he attended a meeting of the T/P/J Science Working Team (SWT) in St.Raphael, France in October. Of particular interest to the PSMSL is the symbiosis between altimetry and tide gauge measurements with gauges being used extensively by the project to calibrate the altimeter data set.

Dr. Woodworth has for the last five years been a member of the Mission Advisory Group (MAG) of the European Space Agency (ESA) Gravity Field and Steady State Ocean Circulation Experiment (GOCE) mission, which is now at the end of the Phase-A development stage. In October, a meeting took place at Granada, Spain at which the scientific arguments of the GOCE MAG, that the mission should progress to a Phase-B with eventual launch in 2004, were accepted by ESA. This is a major development for ocean circulation and sea level studies in the next decade. In April, a meeting organised by Dr. C. Hughes of POL and Prof. C. Wunsch (USA) took place at the Royal Society of London on the use of bottom pressure recorders for validation of temporal gravity change measurements from space. This was followed by the first joint SWT of the US/German Gravity Recovery And Climate Experiment (GRACE). Drs. Hughes and Woodworth have since been admitted formally into the GRACE SWT.

5.3 IUGG'99 and APSG

The University of Birmingham, UK hosted the four-yearly conference of the International Union of Geodesy and Geophysics (IUGG) in July with the PSMSL and GLOSS, and related sea level science, represented strongly in a number of scientific sessions, working groups and business meetings of the various associations (IAPSO and IAG).

In October, Dr. Trevor Baker from POL represented the PSMSL and GLOSS and the sea level group of the Asia Pacific Space Geodynamics (APSG) Project at the GPS'99 Conference in Japan. He presented an overview of the status of GLOSS worldwide and in the region.

6. European Projects

A European Union (EU) funded sea level study called SELF-2 for the Mediterranean was completed during the period with POL participation, with concentration at POL on mean sea level changes, storm surge modelling, absolute gravity and tidal loading. Consultations and site visits which took place with colleagues in Greece some years ago with regard to collaborative upgrading of the Greek tide gauge sites have been resubmitted for possible funding in 2000. The EU EOSS project aims to enhance sea level (tide gauges) and land level (GPS) monitoring, and associated data exchange in Europe, primarily by sets of bilateral (i.e. no new cost) agreements. First activities in this five year project have centred around the North Sea, where most of the countries which have so far signed up to the project commitments are located. Mr. Philip Axe from POL has taken the lead in informing the EOSS group of the activities in PSMSL and GLOSS and in leading Work Package 5 which is associated with data exchange issues. Philip has also attended all twice-yearly Management Meetings. In addition, several other PSMSL-related POL staff have contributed to EOSS activities during the period. It is to be hoped that EOSS will result in the more reliable provision of sea and land level information from the European region. More information on EOSS can be obtained at:

In April, Philip Axe represented the PSMSL and GLOSS at the European Geophysical Society conference at the Hague, Netherlands and gave a presentation on the status of the GLOSS programme. He also represented PSMSL/GLOSS at a scientific sea level workshop in Sardinia, Italy in October.

7. PSMSL/WOCE Centre Staffing

A large number of sea level researchers and data providers corresponded regularly over the years with Mrs. Elaine Spencer who was PSMSL Technical Secretary since 1974. The PSMSL is very much her data set. Unfortunately, both Elaine and her husband, Bob Spencer, who will be well known to PSMSL/GLOSS people through his developments of tide gauges and bottom pressure recorders, decided to take early retirement in May. I am sure that the sincere thanks and best wishes of the sea level community with be extended to them both. Elaine's duties have since been taken over by Mrs. Rose Player who will no doubt become as well known to the community in the future.

In November, Sally Dowell left the WOCE Sea Level Centre at BODC as a result of CCMS staffing rationalisation. Sally is also to be thanked for important contributions to PSMSL/GLOSS during the last decade. Her role has been filled in the short term by a temporary contract position.

On more positive notes, Dr. Simon Williams has been appointed to the GPS and absolute gravity group at POL, which will benefit the land movement studies discussed above. In addition, the appointment of Dr. Thorkild Aarup to the post of GLOSS Technical Secretary at IOC has been a major boost to GLOSS coordination. During 1999, Thorkild (Thor) organised the GE6 meeting in Toulouse and represented GLOSS at a number of international meetings. He can be contacted via

8. Visitors to the PSMSL in 1999

Visitors to the PSMSL during 1999 included Ms. Vibeke Huess (Danish Meteorological Institute), Mr. Pat Caldwell (Univ. of Hawaii Sea Level Center), Mr. Charles Quartley (Valeport Ltd.), Mme. Janice Trotte and Dr. Thorkild Aarup (IOC), Dr. David Pugh (Southampton Oceanography Centre), Dr. Richard Bingley (Univ. of Nottingham), Prof. Mike Bevis (Univ. of Hawaii), Mr. Tran Phuong Dong (Marine Hydro-Meteorological Center, Vietnam) and Dr. David Cartwright (former Director, Bidston Observatory).

9. Publications and Outreach

Some relevant recent publications by Dr. Woodworth and other PSMSL-related staff are included in Appendix 2. In addition, during 1999 a number of seminars were presented to UK universities by PSMSL-related POL staff on the topics of sea level changes, altimetry and space gravity. Dr. Woodworth was appointed Visiting Professor to Liverpool University in November.


It can be seen that 1999 has been a further active year with regard to important workshops, international conferences and working groups. It has been a difficult year with regard to data acquisition due to circumstances beyond our control, but improvements to former levels are expected in 2000. Scientific output, represented by the number of POL publications in sea level and related fields, are as high as ever.

Particular thanks go to members of staff of the Proudman Oceanographic Laboratory (Bidston Observatory) who contribute part of their time to PSMSL activities.

P.L.Woodworth (December 1999)

Appendix 1: Number of station-years entered into the databank for each country or coastline in the period mid-December 1998 to mid-December 1999 (945 total).

 SPITSBERGEN                             		2
 NORWAY                                          	20
 SWEDEN                                          	10
 NETHERLANDS                                     	11
 BELGIUM                                          	6
 UNITED KINGDOM                                  	45
 CHANNEL ISLANDS                                  	1
 FRANCE (ATLANTIC)                               	10
 SPAIN (ATLANTIC)                                	94
 SPAIN (MEDITERRANEAN)                  		19
 SPAIN (BALEARIC ISLANDS)               		3
 ITALY (MEDITERRANEAN)                   		4
 ITALY (ADRIATIC)                                	74
 SLOVENIA                                         	1
 CROATIA                                         	14
 GREECE                                          	17
 TURKEY                                           	3
 ISRAEL (MEDITERRANEAN)                  		2
 SPANISH N. AFRICA                                	6
 SPAIN (CANARY ISLANDS)                  		31
 CAPE VERDE ISLANDS                        		3
 ASCENSION                                        	1
 MOZAMBIQUE                                       	3
 MADAGASCAR                                       	8
 SEYCHELLES                                       	1
 MAURITIUS                                        	2
 CHAGOS ARCHIPELAGO                    			3
 MALDIVES                                         	3
 KENYA                                            	3
 GULF                                            	48
 MUSCAT & OMAN                                 		5
 INDIA                                            	7
 BANGLADESH                                      	23
 THAILAND (ANDAMAN SEA)             			1
 MALAYSIA                                        	12
 VIET NAM                                       	134
 HONG KONG, CHINA                             		7
 JAPAN (HOKKAIDO)                              		5
 JAPAN (HONSHU-PACIFIC)                   		18
 JAPAN (SHIKOKU)                                  	7
 JAPAN (KYUSHU)                                  	8
 JAPAN (AMAMI GUNTO)                       		2
 JAPAN (HONSHU-JAPAN SEA)            			7
 JAPAN (OGASAWARA GUNTO)          			1
 JAPAN (MINAMI-TORI-SHIMA)          			1
 PHILIPPINES                                     	31
 SARAWAK                                          	3
 SABAH                                            	6
 NEW ZEALAND                                      	4
 PALAU ISLANDS                                    	1
 MARSHALL ISLANDS                            		7
 KIRIBATI                                         	3
 TUVALU                                           	1
 NEW CALEDONIA                                    	1
 HAWAIIAN ISLANDS                             		3
 LINE ISLANDS                                     	1
 PENRHYN ISLAND                                   	1
 COOK ISLANDS                                     	2
 GAMBIER ISLAND                                   	1
 EASTER ISLAND                                    	1
 USA (ALASKA)                                    	10
 MEXICO (PACIFIC)                                 	9
 COLOMBIA (PACIFIC)                           		4
 ECUADOR                                          	2
 CHILE                                            	7
 ARGENTINA                                       	16
 BRAZIL                                          	63
 TRINIDAD & TOBAGO                            		2
 COLOMBIA (CARIBBEAN)                   		6
 HONDURAS                                         	3
 BAHAMAS                                          	3
 GREENLAND                                        	4
 ANTARCTICA                                       	6
Appendix 2: Some Relevant Reports dated 1999

Woodworth, P.L., Tsimplis, M.N., Flather, R.A. and Shennan, I. 1999. A review of the trends observed in British Isles mean sea level data measured by tide gauges. Geophysical Journal International, 136, 651-670.

Woodworth, P.L. 1999. High waters at Liverpool since 1768: the UK's longest sea level record. Geophysical Research Letters, 26 (11), 1589-1592.

Shum, C., Tseng, H., Guman, M., Urban, T. and Woodworth, P.L. 1999. Observing long-term mean sea level variations in the China Seas. Submitted to the Journal of Advances in Marine Science and Technology Society. (Paper submitted to PORSEC Conference, China, 1998.)

Woodworth, P.L. 1999. Trends in British Isles mean sea level. Proceedings of the 34th MAFF Conference of River and Coastal Engineers, 30 June to 2 July 1999, Keele University, pp.4.1.1-4.1.13.

Woodworth, P.L., Hughes, C.W., Vassie, J.M., Spencer, R., Whitworth, T. and Peterson, R.G. 1999. Coherence of bottom and sub-surface pressures around Antarctica. To be published by IOC in the Proceedings of the Workshop on Ocean Circulation Science derived from the Atlantic, Indian and Arctic Sea Level Networks, 10-11 May 1999, GRGS Toulouse, France.

Balmino, G., Rummel, R., Visser, P. and Woodworth, P. 1999. Gravity Field and Steady-State Ocean Circulation Mission. Reports for assessment: the four candidate Earth Explorer Core Missions. European Space Agency Report SP-1233(1). 217pp.

Mitchum, G.T., Cheney, R., Fu, L-L., Le Provost, C., Menard, Y. and Woodworth, P.L. 1999. The future of sea surface height observations. Proceedings of the conference on The Ocean Observing System for Climate, St.Raphael, France, 18-22 October 1999. (Solicted papers).

Mitchum, G.T., Cheney, R., Fu, L-L., Le Provost, C., Menard, Y. and Woodworth, P.L. 1999. Sea surface height observations from altimeters and tide gauges. CLIVAR Exchanges, 4(3), 11-16.

Johannessen, J., Le Provost, C., Drange, H., Srokosz, M., Woodworth, P., Schlussel, P., Le Grand, P., Kerr, Y., Wingham, D. and Rebhan, H. 1999. Emerging new Earth Observation capabilities in the context of ocean observing systems for climate. Proceedings of the conference on The Ocean Observing System for Climate, St.Raphael, France, 18-22 October 1999. (Solicted papers).

Woodworth, P.L. 1999. A study of changes in high water levels and tides at Liverpool during the last two hundred and thirty years with some historical background. Proudman Oceanographic Laboratory Report No.56, 62pp. & figures.

Woodworth, P.L. 1999. Report by the PSMSL for the period 1995-99 to the XXII General Assembly of the IUGG, Birmingham, July 1999. (Also to be printed in IAG 'Travaux' series).