PSMSL Annual Report for 1994

This report reviews briefly the work of the Permanent Service for Mean Sea Level (PSMSL) during 1994. This year, the PSMSL databanked its usual large amount of mean sea level data, enhanced significantly its data transfer and information communication methods, and published a number of important scientific and technical reports.

Data Holdings

Almost 1600 station-years of data were entered into the PSMSL database since the last Annual Report (i.e. in the period January to mid-December 1994). This is much less than the record 5000 station-years entered in 1993, but is still more than in a `typical' year. The new sets of data are summarised in Appendix 1 and Figure 1. Amongst the smaller contributions, but of interest given that the PSMSL is based at Bidston, are the first years of data from the tide gauges at Ascension and St.Helena, two of the Proudman Oceanographic Laboratory's upgraded South Atlantic network (Woodworth et al., 1994). The November 1993 version of `Data Holdings of the PSMSL' (Spencer and Woodworth, 1993) was circulated to tide gauge authorities and scientists in early 1994.

Data Transfer Arrangements

After many years, the method of distributing PSMSL data on magnetic tapes in the GF3 format has been discontinued, as most scientists can now access an `Anonymous FTP' server across the Internet. The Internet address is `' (or IP Number and PSMSL data can be found in the directory `/pub/psmsl'. This is the same address as used for FTP datasets by the WOCE Sea Level Centre and the British Oceanographic Data Centre (BODC) and it is used intensively. For example, between mid-July and mid-December, 200 `get' commands were issued to the psmsl directory alone. A disadvantage of FTP access as a means of data exchange, compared to the old arrangement of responding to letters requesting GF3 tapes, is that it is not as easy to keep detailed information on all our customers, although we do keep a list of the remote userid's of people accessing the facility. However, the advantages in terms of providing data instantly, and at virtually zero cost, far outweigh any disadvantages.

For people without access to the Internet, but who have access to a computer with a CDROM drive, the summer 1994 version of the PSMSL dataset is now available on a CDROM produced by the US National Oceanographic Data Center (NODC). The same disk also includes the TOGA sea level dataset from the Hawaii Sea Level Center. We are very grateful to Bruce Douglas and Andy Allegra of NODC for providing the CDROM's which can be obtained from the PSMSL. It is our intention that future versions of the PSMSL dataset will also be available by this means. We shall also continue to provide subsets of the dataset on floppy disk on an ad-hoc basis.

The World Wide Web

The World Wide Web (WWW) provides a facility for people with UNIX workstations or PC's connected to the Internet with a utility such as Mosaic to access a vast amount of information stored on computers around the world.

The PSMSL has provided a prototype set of WWW information called `A Guide to Tide Gauge Networks and Global and Regional Sea Level Data Sets' which can be viewed by opening the file: (DEAD LINK)

This provides information and contact names covering GLOSS, the PSMSL itself, the Hawaii (TOGA) Center, the WOCE Sea Level Centres, Bidston's ACCLAIM programme, and the Australian National Tidal Facility. It describes how data can be obtained, usually via FTP, from each centre. In addition, the PSMSL pages provide a number of maps which describe the dataset in more detail, and which show which regions of the world experienced higher or lower sea levels during the last few years. It is our intention that this facility will develop to serve the requirements of GLOSS and sea level research generally.

Fax Server Facility

A fax server facility has been established at Bidston, and during early 1995 our address lists of tide gauge authorities, GLOSS Contacts and scientists will be updated to include as many fax numbers as possible. It should then be possible to send at regular intervals items of news on PSMSL or GLOSS activities to subsets of the community without the expense and delay involved in writing letters. This facility will complement the electronic mail systems on the Internet, to which most scientists have access but to which most tide gauge authorities have not at present.

GLOSS Status

For the last few 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.

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 1990 or later;

Category 2: 'Probably operational' stations for which the latest data is within the period 1980-1989;

Category 3: 'Historical' stations for which the latest data is earlier than 1980;

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 previous years with the category definitions adjusted backwards one, two, three etc. years appropriately.

Note that earlier we used the `GLOSS90' definition of GLOSS, whereas last year and this we have used `GLOSS93'. However, that does not modify the statistics to a great extent. The general modest improvement in GLOSS status continues.

                               Table 1

                 Number of Stations in Each Category

Category      89       90       91       92       93      94

1             105      133      136      158      177     183
2             51       50       57       46       33      35
3             47       42       36       29       26      26
4             103      81       77       73       72      64

Total         306      306      306      306      308     308

GLOSS Handbook Version 2

Version 2 (March 94) of the `GLOSS Handbook' PC disk file, containing details of each GLOSS gauge, was distributed to all GLOSS Contacts by its editor Dr.Lesley Rickards during the summer. The contents of the Handbook are also available from the PSMSL FTP disk.


Volume 2 of the `IOC Manual on Sea Level Measurement and Interpretation', edited by Mr.David Blackman with contributions from the GLOSS Group of Experts, was printed by IOC in early 1994, together with a reprinting of Volume 1. Copies are available from either the PSMSL or IOC.

A report entitled `Sea Level Changes: Measurements and Analysis', containing abstracts of papers contributed to the sixtieth anniversary meeting of the PSMSL in December 1993, was also printed and circulated in early 1994.

Mrs.Sally Dowell represented the PSMSL at the Small Island Developing States meeting of UNESCO in Barbados, April 1994, and contributed a PSMSL-IOC report on sea level monitoring in the countries represented at the conference. A UNESCO report `Island Agenda', also prepared for the meeting, referred further to sea level monitoring.

A report of the meeting of IAPSO Committee on the Geodetic Fixing of Tide Gauge Bench Marks, 13-15 December 1993, edited by Dr.Bill Carter, has been printed by NOAA and copies will be available from the PSMSL in the New Year.

A report on the precise datum control for pressure tide gauges, derived from Bidston's experiences with pressure gauges in the S.Atlantic, has been accepted for publication.

References to these publications, together with those stemming from scientific analyses of the sea level dataset, are given below.

Related Altimetry Activities

Full participation has been maintained with the ERS-1 and TOPEX/POSEIDON altimeter working groups. Drs.Woodworth and Hughes became Principal Investigators in 1994 for the ERS missions. Dr.Woodworth attended an ERS-2/PRARE meeting in Potsdam in November, and a TOPEX/POSEIDON meeting at the Fall AGU in San Francisco in December.

IPCC 1995

The PSMSL took part in two meetings of the sea level study group of the Intergovernmental Panel on Climate Change (IPCC) during 1994 at Utrecht and Innsbruck. The report of the group, edited by Dr.R.A.Warrick, will be published as a chapter of the full IPCC 1995 report.

European Sea Level Projects

The three sea level and land level (GPS) projects funded by the European Commission referred to in previous annual reports have continued with Drs.Baker and Tsimplis representing PSMSL interests. A number of scientific papers have recently stemmed from this work (see References below). A proposal called `EuroGLOSS', for the effective densification of the GLOSS network in the European region, has been written by Drs.Baker, Woodworth and Blewitt (Newcastle University) and has been submitted to IOC for discussion. Dr.Baker also represented the PSMSL at meetings of the IERS/IGS and WEGENER programmes.


Arrangements have been made with the British Council and the National Institute of Oceanography, India for a technical specialist from the NIO to receive three months tide gauge training at Bidston in 1995.

Directing Board Arrangements

At present, the IAPSO Commission on Mean Sea Level and Tides functions as the PSMSL Directing Board. The Commission consists of its President, Dr.D.T.Pugh (IOSDL, UK) and members Dr.D.E.Cartwright (Petersfield, UK), Dr.G.Mitchum (Univ.of Hawaii, USA), Dr.W.Carter (NOAA, USA), Mesquita (Univ.of Sao Paulo, Brazil), Prof.T.Murty (IOS, Canada moving to NTF, Australia), Dr.C.Boucher (IGN, France), Dr.R.G.Bilham (Univ.of Colorado, USA) and Dr.V.K.Nagar (Survey of India). The Commission has never met formally but conducts business primarily via contacts at other meetings (e.g. GLOSS GE meetings). All members are circulated copies of the PSMSL reports and are asked to advise accordingly.

As IAPSO Commissions are not permanent bodies, discussions have taken place during 1994 on the means by which a more focused PSMSL Advisory Board could be established on a more regular basis. It is intended that the proposal for these new arrangements will be submitted to ICSU/FAGS and IAPSO at the Boulder IUGG 1995 Assembly.

Visitors to the PSMSL

Visitors to the PSMSL during 1994 included Mr.Ole Andersen (Copenhagen University, Denmark), Prof.E.Bird (Melbourne University, Australia), Prof.G.Brundrit (Cape Town University, South Africa), Dr.J.De Ronde and colleagues (Rijkswaterstaat, Netherlands), Dr.G.Kivman (Shirshov Institute, St.Petersburg, Russia), Mr.G.Liebsch (Dresden University, Germany), Dr.E.Marone (Centro de Estudos do Mar, Brasil) and Mr.P.Nwilo (Salford University). Special visits were made by Mr.R.Malpas and Prof.J.Krebs, Chairman and Chief Executive respectively of the UK Natural Environment Research Council, the main funder of PSMSL activities.


It can be seen that 1994, the PSMSL's sixty-first year, has been a notable one for the development of its facilities for distributing data and information to researchers and tide gauge operators, and for publicising its products and services. A more than average amount of data was acquired in the year, which has also been a particularly productive one with regard to the number of scientific and technical publications.

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 1994)

Reports Published in 1994 or Referred to Above

Ashkenazi, V. et al. (many authors including T.F.Baker). 1994. EUROGAUGE: the west European tide gauge monitoring project. To be published in the proceedings of the INSMAP 94 Conference.

Ashkenazi, V. et al. (many authors including T.F.Baker). 1994. UKGAUGE: the United Kingdom tide gauge monitoring project. To be published in the proceedings of the INSMAP 94 Conference.

Baker, T.F., Woodworth, P.L. and Blewitt, G. 1994. A proposal for the definition of a strategic European network for sea level and coastal land level monitoring (EuroGLOSS). Internal document.

Carter, W.E. (ed.) 1994. Report of the Surrey workshop of the IAPSO tide gauge bench mark fixing committee. Report of a meeting held 13-15 December 1993 at IOSDL, UK. NOAA Technical Report NOSOES0006. 81pp.

Dowell, S. 1994. Sea level monitoring in the small island developing states. IOC/INF-954. 24pp.

IOC. 1994. Manual on sea-level measurement and interpretation. Volume 2 - Emerging Technologies. IOC Manuals and Guides No.14. 72pp.

Spencer, N.E. and Woodworth, P.L. 1993. Data holdings of the Permanent Service for Mean Sea Level (November 1993). Bidston, Birkenhead: Permanent Service for Mean Sea Level, 81pp.

Tawn, J.A., Dixon, M.J. and Woodworth, P.L. 1994. Trends in sea levels. pp.147-181 in Statistics for the Environment 2: Water Related Issues, eds. Barnett, V. and Turkman, K.F., John Wiley and Sons Ltd.

Tsimplis, M.N., Flather, R.A. and Vassie, J.M. 1994. The North Sea pole tide described through a tide-surge numerical model. Geophysical Research Letters, 21(6), 449-452.

Tsimplis, M.N. and Vlahakis, G.N. 1994. Meteorological forcing and sea-level variability in the Aegean Sea. Journal of Geophysical Research, 99(C5), 9879-9890.

Tsimplis, M.N. and Woodworth, P.L. 1994. The global distribution of the seasonal sea level cycle calculated from coastal tide gauge data. Journal of Geophysical Research, 99(C8), 16031-16039.

UNESCO. 1994. Island Agenda. An overview of UNESCO's work on island environments, territories, and societies. UNESCO report dated March 1994. 131pp.

Woodworth, P.L. (ed.) 1994. Sea level changes: measurements and analysis. Sixtieth anniversary meeting of the Permanent Service for Mean Sea Level. Bidston, Birkenhead: Permanent Service for Mean Sea Level. 37pp.

Woodworth, P.L., Vassie, J.M., Spencer, R. and Smith, D.E. 1994. Precise datum control for pressure tide gauges. Marine Geodesy (in press).

Appendix 1: Number of station-years entered into the databank for each country or coastline in the period January to mid-December 1994 (1559 total).

FAEROE ISLANDS                    1
SPITSBERGEN                       4
RUSSIA (ARCTIC)                   3
NORWAY                            86
SWEDEN                            70
DENMARK                           15
NETHERLANDS                       11
UNITED KINGDOM                    40
IRELAND                           1
CHANNEL ISLANDS                   1
FRANCE (ATLANTIC)                 25
SPAIN (ATLANTIC)                  1
PORTUGAL                          3
GIBRALTAR                         1
SPAIN (MEDITERRANEAN)             14
ITALY (MEDITERRANEAN)             85
ITALY (ADRIATIC)                  15
GREECE                            100
RUSSIA (BLACK SEA)                1
TURKEY                            4
PORTUGAL (AZORES)                 9
PORTUGAL (MADEIRA)                2
SENEGAL                           1
ASCENSION ISLAND                  1
NIGERIA                           27
ST. HELENA                        1
COMORO ISLANDS                    1
MAURITIUS                         2
CHAGOS ARCHIPELAGO                1
KENYA                             2
SUDAN                             1
GULF                              129
INDIA                             17
MALAYSIA                          12
SINGAPORE                         14
CHINA                             50
RUSSIA (PACIFIC OCEAN)            16
JAPAN (HOKKAIDO)                  16
JAPAN (HONSHU-PACIFIC)            54
JAPAN (SHIKOKU)                   18
JAPAN (KYUSHU)                    22
JAPAN (AMAMI GUNTO)               6
PHILIPPINES                       9
SARAWAK                           1
SABAH                             2
AUSTRALASIA                       1
NEW ZEALAND                       4
MARIANAS ISLANDS                  2
CAROLINE ISLANDS                  3
MARSHALL ISLANDS                  5
GILBERT ISLANDS                   1
TUVALU                            1
SOLOMON ISLANDS                   1
NEW CALEDONIA                     2
AMERICAN SAMOA                    2
PHOENIX ISLANDS                   1
HAWAIIAN ISLANDS                  15
LINE ISLANDS                      2
ILES DE LA SOCIETE                2
USA (ALASKA)                      24
USA (PACIFIC COAST)               40
MEXICO (PACIFIC)                  1
COSTA RICA (PACIFIC)              3
PANAMA (PACIFIC)                  3
COLOMBIA (PACIFIC)                6
ECUADOR                           1
PERU                              3
CHILE                             2
ARGENTINA                         5
FRENCH GUIANA                     3
COLOMBIA (CARIBBEAN)              3
PANAMA (CARIBBEAN)                1
COSTA RICA (CARIBBEAN)            10
BARBADOS                          2
CAYMAN ISLANDS                    6
PUERTO RICO                       6
VIRGIN ISLANDS                    6
USA (GULF)                        44
BAHAMAS                           2
BERMUDA                           4
USA (ATLANTIC)                    76
GREENLAND                         4
ANTARCTIC                         15