This report reviews briefly the work of the Permanent Service for Mean Sea Level (PSMSL) during 2001. In this period, the 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 and geophysics.

The PSMSL is operated at the Proudman Oceanographic Laboratory (POL), Bidston Observatory under the auspices of the International Council for Science (ICSU), and is a member of the Federation of Astronomical and Geophysical Data Analysis Services (FAGS). The PSMSL reports to the International Association for the Physical Sciences of the Ocean Commission on Mean Sea Level and Tides (IAPSO/CMSLT) and has an Advisory Board consisting of scientists expert in each area of sea level research. Annual reports on the work of the PSMSL are circulated each year to the International Association of Geodesy (IAG), the Intergovernmental Oceanographic Commission (IOC), IAPSO, FAGS, and other relevant bodies and are available publicly via the web at:

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

This same web page also serves as a source of PSMSL data and ancillary information.

2. PSMSL Data Receipts for 2001

In the period since the last Annual Report (i.e. since mid-December 2000), almost 1500 station-years of data were entered into the PSMSL database which is several 100 more than in each of the previous two years. Appendix 1 lists countries from which sea level data were obtained, while Figure 1 shows their locations. Significant data sets can be seen to have originated from Europe (notably from Spain), Canada, Korea, Australia and Venezuela, with major gaps as in previous years in South America and Africa. There is a clear long-standing problem with the availability of data from these regions which is discussed further below.

The Global Sea Level Observing System (GLOSS) is an IOC programme, 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) with the PSMSL taking the lead role in its development. The GIP calls for the development of a GLOSS Core Network (GCN) of 287 stations; a network of several tens of sites for on-going satellite altimeter calibration (GLOSS-ALT); a programme of investment in gauges with geodetic equipment (especially GPS) at sites with long records (the LTT, or long term trends, set); and the use of gauges at straits and other strategic locations for ocean circulation monitoring (the OC set).

The GLOSS programme is now operated under the auspices of the new Joint Commission for Oceanography and Marine Meteorology (JCOMM) of IOC and the World Meteorological Organisation (WMO), rather than the IOC alone, following major changes to the organisational structures of the programmes of both organisations.

A review of GLOSS Core Network (GCN) status as of October 2001 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, with the GLOSS Core Network considered to be approximately two-thirds operational, if one uses data receipts by the PSMSL as a guide to operational status. The apparent status will appear to improve in the near future, once the definition of the GCN network is revisited next year. The PSMSL has during the year worked closely with the IOC GLOSS Technical Secretary (Dr. Thorkild Aarup) to investigate possibilities for obtaining additional funding for the programme (see below).

No IOC-funded GLOSS training courses took place during 2001, although a sea level course related to GLOSS took place in May in Guatemala for Central American countries attended by Dr. Pat Caldwell (University of Hawaii) with some PSMSL input. However, several courses are planned for 2002-03 in different countries.

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.

A joint project between the IOC International Oceanographic Data and Information Exchange (IODE) Committee and GLOSS to conduct a 'data archaeology' survey of historical sea level records, as described in the 2000 PSMSL Annual Report, was begun by Dr. Lesley Rickards. This project has the aim of extending existing time series and gaining access to observations which are not in digital form. The GLOSS Secretariat has encouraged 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.

The 7^th meeting of the GLOSS Group of Experts took place during the week of 23^rd April hosted by the University of Hawaii. The main workshops of the week comprised:

• A scientific symposium in honour of Prof. Klaus Wyrtki, attended by many of his friends and former colleagues. Klaus and some of his Hawaii co-workers were presented with 'GLOSS certificates' as a mark of appreciation of their work for the programme. The symposium was organised by Prof. Mark Merrifield and others.
• A meeting of the Asia-Pacific Space Geodynamics programme, organised by Prof. C.K. Shum and others. Presentations were made on work using tide gauge, altimeter and other data sets in the region.
• A meeting of the International Association of Geodesy GPS-Water Level Measurements group (SSG 2.194), organised by Dr. Doug Martin and others.
• A working meeting of the PSMSL/IGS/GLOSS/IAG/IAPSO group on the operation of Continuous GPS at Tide Gauges (CGPS@TG), chaired by Prof. Mike Bevis. This reviewed developments in GPS and other geodetic techniques at gauges. The meeting also initiated the TIGA-PP (Tide Gauges-GPS-Pilot Project) under the auspices of the International GPS Service and with main contact Dr. Tilo Schoene (GFZ, Germany).
• The 7^th GLOSS Experts meeting itself, for which a reports is available from IOC in electronic and printed form. Main items concerned national and international developments, the availability of tidal constants, data archaeology, the work of the GLOSS Scientific Sub-Group, interactions between the IOC Coastal Ocean Observations Panel (COOP) and GLOSS, the GLOSS Handbook, capacity building, relevant meetings, and new resources for GLOSS. Of particular importance was the need for the 'fast GLOSS' (formerly the 'fast WOCE') data stream to become even faster and plans were made for IOC, PSMSL, University of Hawaii and others to work towards that goal.

The Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC) was published during 2001 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.

Participation has continued in US and European altimeter working groups during the period, including those of TOPEX/POSEIDON, JASON-1 (launched 7 December), ERS and the upcoming 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. During 2001, 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. This resulted in one paper being accepted for publication in Marine Geodesy with other work in progress. 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.

• European Science Foundation meeting on Glacial-International Sea Level Change in Four Dimensions at St. Andrews, Scotland (March).
• Joint Commission on Oceanography and Marine Meteorology (JCOMM-1) in Akureyi, Iceland (June). This important meeting laid the basis for oversight of many IOC and WMO activities for the next few years. A report by the PSMSL to the meeting can be found at

• IOC Assembly (July)
• Briefing meeting for the UK Chief Scientist (Prof. David King) on matters associated with climate change (July).
• Coastal Ocean Advanced Scientific and Technical Studies (COASTS) workshop at UNESCO, Paris (August).
• British Association for the Advancement of Science in Glasgow (September).
• British Cartographic Society in Liverpool (September).

• Final meeting of the European Union (EU) EOSS project in Dubrovnik, Croatia (September). This meeting included discussions for the formation of a European Sea Level Service (ESEAS) which it is hoped will attract EU funding in 2001.
• Royal Society Discussion Meeting on issues connected with flooding (November).

At all of these meetings, presentations were given on aspects of sea level changes by PSMSL staff. In addition, the PSMSL was represented at the following meetings:

• International Association of Geodesy at Budapest, Hungary (September). A PSMSL report was provided to the meeting.
• IOC GOOS-Africa Conference in Nairobi, Kenya (November). The PSMSL provided a position paper to the conference on the status of sea level monitoring in Africa (see reference list below) and was represented by Dr. Alex Souza (POL) and IOC staff. The conference initiated important developments towards the future funding of gauges in the continent.

Of particular note during 2001 was the MBE (Member of the British Empire) awarded by the Queen to Mrs. Elaine Spencer in the 2001 New Year's Honours List. Elaine was PSMSL Technical Secretary between 1974 and 1999 (being replaced by Mrs. Rose Player). The development of the PSMSL data set formed part of the citation for the award.

Also in 2001, Philip Axe, who worked with the PSMSL for several years until 2000 and who is now based at the University of Umea in Sweden, was awarded a Ph.D by Plymouth University.

Dr. Ian Vassie of POL, who was responsible for the development of the UK's South Atlantic tide gauge network and who contributed to many GLOSS training courses, retired in December. He was presented with a 'GLOSS certificate'

The Director of POL (Prof. A.E.Hill) and the UK Natural Environment Research Council have approved the replacement of Ian Vassie's important post, and the addition of an extra post at the PSMSL, by the appointment of two young scientists during 2002.

The PSMSL is responsible to the IAPSO Commission on Mean Sea Level and Tides for the maintenance of the data base of pelagic (bottom pressure recorder) information. This data base, called GLOUP (Global Undersea Pressures), was maintained during the year by Dr. Chris Hughes and can be inspected at:

http://www.pol.ac.uk/psmslh/gloup/gloup.html

In April, Dr. Woodworth described the history of tidal and sea level science at POL and PSMSL on the BBC 'Open Country' programme.

Visitors to the PSMSL during the year included Dr. Lucy Mathers (Delft University of Technology), Dr. David Pugh (Southampton Oceanography Centre), Mr. Richard Hardman (Chair UK Natural Environment Research Council Science & Technology Board), Dr. Bruce Parker (US National Oceanic and Atmospheric Administration), Prof. Carl Wunsch (Massachusetts Institute of Technology), Dr. Michael Tsimplis (Southampton Oceanography Centre), Dr. Michael Reidy (University of Minnesota), Captain Mark Windsor (Royal Navy), Commodore Richard Willis (RN Rtd.), Prof. Michael Hughes (Imperial College, London), Prof. Richard Greatbatch (Dalhousie University, Canada) and Prof. Keith Haines (Reading University, UK).

It can be seen that 2001 has been a further active year with regard to important workshops, international conferences and working groups. Scientific outputs, represented by the number of POL publications in sea level and related fields, are as high as ever.

Particular thanks as usual go to Mrs. Rose Player (PSMSL Technical Secretary) and to members of staff of the Proudman Oceanographic Laboratory (Bidston Observatory) who contribute part of their time to PSMSL activities.

P.L.Woodworth (December 2001)

Appendix 1: Number of station-years entered into the databank for each country or coastline in the period mid-December 2000 to mid-December 2001 (1474 total).

ICELAND                                          	1
SPITSBERGEN                                      	3
RUSSIAN FED.(ARCTIC)                             	2
NORWAY                                           	21
SWEDEN                                           	10
POLAND                                           	12
GERMANY (NORTH SEA)                              	3
NETHERLANDS                                      	11
BELGIUM                                          	3
UNITED KINGDOM                                   	44
IRELAND                                          	4
CHANNEL ISLANDS                                  	1
FRANCE (ATLANTIC)                                	12
SPAIN (ATLANTIC)                                 	114
PORTUGAL                                         	15
GIBRALTAR                                        	4
SPAIN (MEDITERRANEAN)                            	39
FRANCE (MEDITERRANEAN)                           	4
MALTA                                            	6
ITALY (ADRIATIC)                                 	73
SLOVENIA                                         	1
CROATIA                                          	16
GREECE                                           	20
RUSSIAN FED. (BLACK SEA)                         	2
GEORGIA                                          	4 
ISRAEL (MEDITERRANEAN)                           	4
ASCENSION                                        	1
MOZAMBIQUE                                       	4
CROZET IS.                                       	5
KERGUELEN ISLAND                                 	8
SAINT PAUL ISLAND                                	7
MAURITIUS                                        	4
CHAGOS ARCHIPELAGO                               	1
MALDIVES                                         	4
TANZANIA                                         	12
KENYA                                            	2
MUSCAT & OMAN                                    	2
INDIA                                            	35
THAILAND (ANDAMAN SEA)                           	3
MALAYSIA                                         	12
SINGAPORE                                        	20
THAILAND (G. OF THAILAND)                        	15
HONG KONG, CHINA                                 	6
KOREA (SOUTH)                                    	66
RUSSIAN FED. (PAC. OCEAN)                        	4
JAPAN (HOKKAIDO)                                 	5
JAPAN (HONSHU-PACIFIC)                           	18
JAPAN (HONSHU-INLAND SEA)                        	7
JAPAN (SHIKOKU)                                  	7
JAPAN (KYUSHU)                                   	8
JAPAN (AMAMI GUNTO)                              	2
JAPAN (HONSHU-JAPAN SEA)                         	7
JAPAN (OGASAWARA GUNTO)                          	1
JAPAN (MINAMI-TORI-SHIMA)                        	1
SARAWAK                                          	2
SABAH                                            	6
PAPUA NEW GUINEA                                 	2
AUSTRALIA                                        	134
NEW ZEALAND                                      	1
NORTHERN MARIANA IS.                             	1
GUAM                                             	1
CAROLINE IS (FED. STATES OF MICRONESIA)          	4
PALAU ISLANDS                                    	2
MARSHALL ISLANDS                                 	4
KIRIBATI                                         	2
TUVALU                                           	2
NEW CALEDONIA                                    	1
VANUATU                                          	1
FIJI                                             	2
TONGA                                            	1
AMERICAN SAMOA                                   	1
WESTERN SAMOA                                    	1
PHOENIX ISLANDS (KIRIBATI)                       	2
HAWAIIAN ISLANDS                                 	8
LINE ISLANDS                                     	1
PENRHYN ISLAND                                   	1
ILES DE LA SOCIETE                               	1
COOK ISLANDS                                     	2
GAMBIER ISLAND                                   	1
USA (ALEUTIAN ISLANDS)                           	2
USA (ALASKA)                                     	15
CANADA (PACIFIC COAST)                           	136
USA (PACIFIC COAST)                              	20
MEXICO (PACIFIC)                                 	1
EL SALVADOR                                      	27
COLOMBIA (PACIFIC)                               	2
ECUADOR                                          	6
PERU                                             	18
CHILE                                            	4
FALKLAND ISLANDS (MALVINAS)                      	1
BRAZIL                                           	47
VENEZUELA                                        	89
COLOMBIA (CARIBBEAN)                             	2
BARBADOS                                         	3
GUADELOUPE                                       	6
BELIZE                                           	4
CUBA                                             	3
PUERTO RICO                                      	2
VIRGIN ISLANDS                                   	2
USA (GULF)                                       	19
BAHAMAS                                          	1
USA (ATLANTIC)                                   	38
CANADA (ATLANTIC & ARCTIC)                       	138
ANTARCTICA                                       	8

Appendix 2: Some Relevant Reports dated 2000-2001

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. (In press. Available meanwhile as a web document).

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 SeaLevel 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).

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.

Dated 2001

Aarup, T., Adekoya, A., Aman, A., Brundrit, G., Magori, C. and Woodworth, P.L. 2001. Position Paper on the Status of GLOSS in Africa. Contributed to the GOOS-AFRICA Meeting, 19-23 November 2001, Nairobi, Kenya. Intergovernmental Oceanographic Commission, report IOC/INF-1165.

Baker, T.F., Blackman, D.L., Flather, R.A., Vassie, J.M. and Woodworth, P.L. 2001. Integrated effects of climate change on coastal extreme sea levels. To be published in the proceedings of the MAFF 2001 Conference, Keele University, July 2001.

Church, J.A., Gregory, J.M., Huybrechts, P., Kuhn, M., Lambeck, K., Nhuan, M.T., Qin, D. and Woodworth, P.L. 2001. Changes in sea level. In, Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. (eds. J.T. Houghton, Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell and C.A. Johnson). Cambridge: Cambridge University Press. 881pp.

Dong, X., Woodworth, P.L., Moore, P. and Bingley, R. 2001. Absolute calibration of the TOPEX/POSEIDON altimeters using UK tide gauges, GPS and precise, local geoid-differences. Marine Geodesy (in press).

Flather, R.A, Baker, T.F., Woodworth, P.L., Vassie, I.M. and Blackman, D.L. 2001. Integrated effects of climate change on coastal extreme sea levels. POL Internal Document No.140. pp.20.

Heilmann, J., Aarup, T. and Woodworth, P.L. 2001. The Global Sea Level Observing System. Ports and Harbors (Newsletter of the Association of Ports and Harbors), December 2001, 13-15.

Mathers, E.L. and Woodworth, P.L. 2001. Departures from the local inverse barometer model observed in altimeter and tide gauge data and in a global barotropic numerical model. Journal of Geophysical Research, 106(C4), 6957-6972.

Rummel, R., Balmino, G., Johannessen, J.A., Visser, P. and Woodworth, P. 2001. Dedicated gravity field missions - principles and aims. Journal of Geodynamics (in press).

Woodworth, P.L., Le Provost, C., Rickards, L.J., Mitchum, G.T. and Merrifield, M. 2001. A review of sea-level research from tide gauges during the World Ocean Circulation Experiment. Oceanography and Marine Biology: An Annual Review. (in press).

Woodworth, P.L. and Blackman, D.L. 2001. Changes in extreme high waters at Liverpool since 1768. International Journal of Climatology (in press).