This year the Permanent Service for Mean Sea Level (PSMSL) has continued with its primary task of assembly of the global data set of sea level change information and its dissemination to the research community. It has also contributed strongly to the further development of the Global Sea Level Observing System (GLOSS), and has participated in important international conferences and working groups concerned with sea level and climate change. These and other activities are reviewed briefly in the following report.

2. PSMSL Data Receipts for 2000

In the period since the last Annual Report (i.e. since mid-December 1999), almost 1300 station-years of data were entered into the PSMSL database which is approximately 400 more than in 1999. This is a creditable achievement, given the local difficulties referred to in last year's PSMSL Report, with the number of station-years this year similar to those obtained on average prior to 1999.

Appendix 1 lists countries from which sea level data were obtained, while Figure 1 shows their locations. Most data can be seen to have originated from Europe, North America, Japan, Australia and the Pacific, with major gaps in South America, Africa and parts of Asia which will require special attention in 2001. A notable addition to the data set has come from a long record (47 years) from Santos, Brazil contributed by the University of Sao Paulo.

To some extent, the regional gaps can be considered to be a fluctuation, as data have been received from some stations in these regions in previous years. In addition, data from several stations (e.g. from India) are awaiting checking prior to entry into the data base. Nevertheless, there is clearly a long-standing problem with the availability of data from these regions which will require investment both nationally and internationally (e.g. through GLOSS, see below).

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).

For several years, 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.

A review of GLOSS status as of October 2000 can be found at:

http://www.pol.ac.uk/psmsl/programmes/gloss.info.html

In brief, the status of the programme at the present time is near-identical to that one year ago. GLOSS can be considered approximately two-thirds operational, if one uses data receipts by the PSMSL as a guide to operational status, or somewhat better if one considers several factors discussed in detail in the PSMSL 1999 Report. However, these status summaries hide major problems in several regions, with expenditure in new tide gauge equipment in a number of countries, and the network improvements which result, balanced against the fact that many GLOSS stations in other countries are being terminated or require major upgrades. In addition, the investments made in gauges for international programmes (notably WOCE) are unlikely to be repeated in future. Consequently, it is possible that GLOSS status, measured in terms of PSMSL receipts, may have reached a plateau.

This pessimism is contradicted to some extent by the stated requirements for investment in regional networks of coastal tide gauges by, for example, the GOOS COOP (Coastal Oceans Observations Panel). Therefore, GLOSS status may receive a boost in the long term from 'coastal', rather than 'climate' or 'oceanographic', applications. Whatever the scientific emphasis, investment in equipment and training is a priority in many countries. During the past year, the PSMSL has been working closely with the IOC GLOSS Technical Secretary (Dr. Thorkild Aarup) to investigate possibilities for obtaining additional funding for the programme. Results in this area will be reported to the GLOSS Experts meeting in 2001 (see below).

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), Proudman Oceanographic Laboratory (POL), UK (1997), Cape Town, South Africa (1998) and Sao Paulo, Brazil (1999). A further course took place during 15-19 April at Jeddah, Saudi Arabia funded by the Programme for the Environment of the Red Sea and Gulf of Aden (PERSGA) and IOC. The local organisation was led by Dr. Dirar Nasr of PERSGA and IOC provided support for Mr. David Dixon (Plymouth, U.K.) to provide lectures on background sea level science (climate change, oceanography), the need for related geodetic measurements, and 'hands on training sessions' (HOTS) using many training materials from previous courses.

The PSMSL maintains a list of reports relevant to the development of GLOSS at:

http://www.pol.ac.uk/psmsl/training/gloss.pub.html

During the past year, many of these reports have become available in PDF (Acrobat) format down-loadable from the IOC and/or UNESCO electronic libraries. See the above web file for which reports are available this way.

Sea level researchers will be familiar with the GLOSS Handbook product available on the web at the address given in Section 3.1. This product is edited by Dr. Lesley Rickards of the British Oceanographic Data Centre (BODC). Lesley has now commenced major updates towards a 2000-01 version. GLOSS Contacts can be expected to be asked to provide information.

An updated version of the third volume of the IOC Manuals and Guides No.14 on sea level measurement and interpretation has been completed and can be down-loaded from the PSMSL training web page:

http://www.pol.ac.uk/psmsl/training/training.html

which also contains an extensive set of other sea-level related information.

Version 2.0 of the WOCE Sea Level Data set is now available. In addition to the 'Fast-delivery' and 'Delayed-mode' WOCE sea level data sets, the CD-ROM contains tidal constants from the WOCE sea level data set, PSMSL monthly and annual mean sea level data set, and the GLOSS Station Handbook (Version 4.1). Copies are available from PSMSL, BODC or the University of Hawaii Sea Level Center.

The Sea Level CD-ROM is a contribution to the WOCE Global Data (Version 2.0) CD-ROM set (15 CDs). Copies of the complete set are available from the US National Oceanographic Data Center, Silver Spring, USA.

At the recent IOC International Oceanographic Data and Information Exchange (IODE) XVI Committee meeting several extensions to the Global Ocean Data Archaeology and Rescue (GODAR) project led by Mr. Syd Levitus (Ocean Climate Laboratory, WDC-A) were suggested. Dr. Lesley Rickards represented the PSMSL at this meeting and proposed a data archaeology project for historical sea level records with the aim of extending existing time series and gaining access to observations which are not in digital form. In many countries there are considerable amounts of historical sea level data in paper form such as charts or tabulations. These need to be computerised to provide electronic access, as backup for data security, and so that they can be subject to modern quality control and analysis. The original records would not be destroyed, as they may contain further information which is not captured by the computerised version (for example, charts digitised to hourly values might miss tsunami or seiche information) and also, in some cases, they are historic documents.

The IODE Committee supported the proposal and recommended that the sea level archaeology project should be co-ordinated by GLOSS, with the GODAR Project Leader acting as advisor to the project. The GLOSS Secretariat will now encourage all countries to assess their holdings of historical tide gauge data which can potentially be rescued and convey that information to the PSMSL, which will act as a contact point. Following on from this, IOC/GLOSS will aim to put countries in touch with each other and with sea level organisations with regard to collaborative data rescue.

Meetings of the GLOSS Group of Experts (GE) usually take place at intervals of two years. The last (GE6) took place in Toulouse, France in May 1999 and included 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 report of the GE6 meeting can be found in electronic form via the web address in Section 3.1, while the report of the 'Mitchum workshop' is in press.

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). This group has since been formed, with Dr. Mitchum as Chairman, and with representatives of each of the main areas of research in GLOSS. The group will advise the GE as appropriate as scientific priorities develop in future.

Attention is now turning to the organisation of GE7 which will be held at the University of Hawaii during the week of 23 April 2001. This week will follow the successful format of the week of meetings in Toulouse. It will include a scientific workshop entitled 'The Klaus Wyrtki Workshop: Observations and Integrations' concentrating on sea level science in the Pacific and held in honour of Professor Wyrtki, a further workshop concerning sea level aspects of the Asia-Pacific Space Geodynamic Project (APSG), and a workshop on GPS at tide gauges. For more details, see:

http://www.pol.ac.uk/psmsl/ge7/ (DEAD LINK)

The Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) has continued under development in 2000 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. Chapter meetings took place in New Zealand in February and Canada in July with final publication of the TAR in January 2001.

In May, Dr. Woodworth attended the Coordination Meeting of the MedGLOSS programme at Haifa, Israel organised by Dr. Dov Rosen. MedGLOSS is a joint programme of the International Commission for the Scientific Exploration of the Mediterranean Sea (CIESM) and IOC and aims to install and coordinate a network of gauges for the Mediterranean and Black Seas.

In June, Dr. Woodworth represented GLOSS at the second Transition Planning Meeting of the Joint IOC/WMO Technical Commission for Oceanography and Marine Meteorology (JCOMMTRAN-2), the first having been in St.Petersburg, Russian Federation in 1999 at which GLOSS was represented by Dr. Oleg Zilberstein. This second meeting was charged with construction of the essential documents for the first meeting of JCOMM itself in Iceland in June 2001 at which many of the activities of IOC and the World Meteorological Organisation (WMO) will be combined in one framework.

In April, Dr. Woodworth presented an overview of sea level and space gravity science at the Geosciences 2000 conference at Manchester, U.K. In September, he gave a presentation on the monitoring and predicting of long term sea level changes at the Eurocoast 2000 conference in Dubrovnik, Croatia.

In November-December, Dr. David Pugh represented the PSMSL at a meeting of oceanographic institutes (POGO) in Sao Paulo, Brazil and gave a presentation on sea level and climate changes. Shortly afterwards, he have a lecture at the MarCUBA conference in Cuba on climate and sea level trends.

Participation has continued in US and European altimeter working groups during the period. Dr. Woodworth is a Principal Investigator for the TOPEX/POSEIDON and JASON-1 missions and a Co-Investigator for the ERS and Envisat missions. Of particular interest to the PSMSL is the symbiosis between altimetry and tide gauge measurements with gauges being used extensively by the projects to calibrate the altimeter data sets. In December, Dr. Xiaojun Dong from the Shanghai Astronomical Observatory joined the sea level group at POL through a Fellowship from the Royal Society, with the object of researching the best methods for ongoing altimeter calibration using tide gauge data.

Interest has also continued in upcoming space gravity missions including the Gravity Recovery And Climate Experiment (GRACE) mission and the Gravity Field and Steady State Ocean Circulation Experiment (GOCE) mission. Drs. Hughes and Woodworth are closely involved in both these projects.

For the past four years, the European Union (EU) EOSS project has aimed 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. The project (chaired by Prof. H-P. Plag from Norway) ends in September 2001 with an international conference in Dubrovnik, Croatia. Details on that conference can be obtained from plag@statkart.no while a position paper on the status of sea level recording in Europe can be obtained from:

 ICELAND                                         	2
 SPITSBERGEN                                     	1
 NORWAY                                          	23
 SWEDEN                                          	11
 POLAND                                          	12
 GERMANY (NORTH SEA)                             	3
 NETHERLANDS                                     	11
 BELGIUM                                         	3
 UNITED KINGDOM                                  	90
 CHANNEL ISLANDS                                 	3
 FRANCE (ATLANTIC)                               	2
 SPAIN (ATLANTIC)                                	10
 SPAIN (MEDITERRANEAN)                           	40
 FRANCE (MEDITERRANEAN)                          	20
 ITALY (ADRIATIC)                                	40
 SLOVENIA                                        	1
 GREECE                                          	20
 TURKEY                                          	4
 ISRAEL (MEDITERRANEAN)                          	5
 PORTUGAL (AZORES)                               	2
 SPAIN (CANARY ISLANDS)                          	16
 CAPE VERDE ISLANDS                              	1
 SENEGAL                                         	1
 ASCENSION                                       	3
 ST. HELENA                                      	3
 NAMIBIA                                         	6
 SOUTH AFRICA                                    	33
 MALAYSIA                                        	12
 HONG KONG, CHINA                                	7
 JAPAN (HOKKAIDO)                                	7
 JAPAN (HONSHU-PACIFIC)                          	25
 JAPAN (HONSHU-INLAND SEA)                       	8
 JAPAN (SHIKOKU)                                 	8
 JAPAN (KYUSHU)                                  	11
 JAPAN (AMAMI GUNTO)                             	3
 JAPAN (HONSHU-JAPAN SEA)                        	17
 JAPAN (OGASAWARA GUNTO)                         	1
 JAPAN (MINAMI-TORI-SHIMA)                       	1
 SARAWAK                                         	2
 SABAH                                           	6
 PAPUA NEW GUINEA                                	10
 AUSTRALIA                                       	312
 NEW ZEALAND                                     	4
 GUAM                                            	1
 CAROLINE IS (FED. STATES OF MICRONESIA)         	1
 NAURU                                           	2
 MARSHALL ISLANDS                                	11
 KIRIBATI                                        	8
 TUVALU                                          	7
 SOLOMON ISLANDS                                 	2
 VANUATU                                         	7
 FIJI                                            	10
 TONGA                                           	7
 AMERICAN SAMOA                                  	2
 WESTERN SAMOA                                   	7
 HAWAIIAN ISLANDS                                	14
 ILES DE LA SOCIETE                              	2
 COOK ISLANDS                                    	7
 USA (ALEUTIAN ISLANDS)                          	4
 USA (ALASKA)                                    	30
 CANADA (PACIFIC COAST)                          	39
 USA (PACIFIC COAST)                             	67
 MEXICO (PACIFIC)                                	2
 CHILE                                           	2
 ARGENTINA                                       	2
 FALKLAND ISLANDS (MALVINAS)                     	2
 BRAZIL                                          	47
 CUBA                                            	30
 PUERTO RICO                                     	4
 VIRGIN ISLANDS                                  	4
 USA (GULF)                                      	42
 BAHAMAS                                         	2
 BERMUDA                                         	2
 USA (ATLANTIC)                                  	83
 CANADA (ATLANTIC AND ARCTIC)                    	16
 ANTARCTICA                                      	6

Appendix 2: Some Relevant Reports dated 1999-2000

Dated 1999

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.

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).

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.

Smith, A.J.E., Ambrosius, B.A.C., Wakker, K.F., Woodworth P.L. and Vassie, J.M. 1999. Ocean tides from harmonic and response analysis on TOPEX/POSEIDON altimetry. Advances in Space Research, 22, 1541-1548.

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 printed in IAG 'Travaux' Volume 39 (1995-1999) produced on cdrom by the IAG.

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.

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.

Dated 2000

IOC. 2000. Manual on sea-level measurement and interpretation. Volume 3 - Reappraisals and recommendations as of the year 2000. Intergovernmental Oceanographic Commission Manuals and Guides No. 14. IOC, Paris.

Mathers, E.L. and Woodworth, P.L. 2000. Departures from the local inverse barometer model observed in altimeter and tide gauge data and in a global barotropic numerical model. To be published in the Journal of Geophysical Research.

Raper, S.C.B., Woodworth, P.L. and 7 others. 2000. Global changes in the volume and mass of the ocean. pp. 9-80 in Sea Level Change and Coastal Processes: Implications for Europe (eds. D. Smith, S. Raper, S. Zerbini, and A. Sanchez-Arcilla), Luxembourg: Office for Official Publications of the European Communities. 247pp.

Shum, C.K., Zhao, C.Y., Tseng, H.Z. and Woodworth, P. 2000. Twentieth century sea level change in the Pacific basin. Proceedings of the Pacific Islands Conference on Climate Change, Climate Variability and Sea Level Rise, 2-7 April, 2000, National Auditorium, Rarotonga, Cook Islands. (In press).

Tsimplis, M.N. and Baker, T.F. 2000. Sea level drop in the Mediterranean Sea: an indicator of deep water salinity and temperature changes? Geophysical Research Letters, 27 (12), 1731-1734.

Visser, P.N.A.M., Rummel, R., Balmino, G., Sunkel, H., Johannessen, J., Aguirre, M., Woodworth, P.L., Le Provost, C., Tscherning, C.C. and Sabadini, R. 2000. The European Earth Explorer Mission GOCE: impact for the geosciences. To be published in, Glacial isostatic adjustment and the Earth system: sea-level, crustal deformation, gravity and rotation (American Geophysical Union).

Woodworth, P.L. 2000. Monitoring and predicting long term sea level changes. Periodicum Biologorum Vol. 102, Supplement 1, 665-672.

Woodworth, P.L. 2000. The journals of William Hutchinson. East Ardsley, Wakefield: Microform Academic Publishers. 15pp. and microfilm.

Zerbini. S., Baker, T.F. and 9 others. 2000. Regional and local sea level variations. pp. 81-133 in in Sea Level Change and Coastal Processes: Implications for Europe (eds. D. Smith, S. Raper, S. Zerbini, and A. Sanchez-Arcilla), Luxembourg: Office for Official Publications of the European Communities. 247pp.