The British Oceanographic Date Centre (BODC) has responsibility for assembling, quality controlling and disseminating the comprehensive sea level data set for WOCE. It began its activities in early 1991 and is at present collating data from approximately 176 tide gauge sites worldwide.

Data have been supplied to the DAC by Argentina, Australia, Chile, China, Cuba, Denmark (including Greenland), Ecuador, France, Guinea, Korea, Iceland, Japan, New Zealand, Peru, Philippines, Portugal, Russia, South Africa, Spain, the U.K. and the U.S.A. from approximately 160 tide gauges. The total volume of data received so far is over 3000 site years. Over the last year 336 site years of data were added to the databank from 33 sites. A further 130 site years from 95 sites are presently undergoing quality control. Data supply is generally quite good, data suppliers appreciate a reminder to forward the data, but then send them quite promptly. Most sites have data from 1985 onwards, but some go back to almost the beginning of the century.

BODC also assists in the management of the data from the POL ACCLAIM (Antarctic Circumpolar Current Levels by Altimetry & Island Measurements) network in the South Atlantic. This includes 7 island and Antarctic tide gauges and, in addition, bottom pressure gauge data from deployments at about 20 locations (45 records, each usually of approximately 1 year in length, have been collected so far).

BODC have developed EDTEVA, a sophisticated software system, to carry out quality control on the data. In addition to the rapid visualisation of the data, it incorporates tidal analysis, time shifting, datum shifting, gap filing, data value flagging, and the production of daily and monthly means. Data documentation is compiled, with special attention paid to benchmark and datum history information.

In October 1997, a paper was presented to the Ocean Data Symposium, jointly by both of the WOCE Sea Level Data Assembly Centres on 'Developments in Sea Level Data Management and Exchange'. Copies can be downloaded from the BODC Web site and following the links to the WOCE Sea Level DAC pages (http://www.pol.ac.uk/bodc/bodcmain.html. This paper summarised the work of the two DACs, discussed their data holdings and quality assurance procedures and considered how sea level data might be managed in the future (based on the GLOSS implementation plan).

In 1998, a CD-ROM was produced containing all of the data collected by the WOCE 'delayed-mode' Sea Level DAC. This CD-ROM formed one of the WOCE set of CD-ROMs made available at the WOCE Scientific Conference 'Ocean Circulation and Climate' in Halifax, Canada (May 1998). The CD-ROM was a collaborative effort, and includes the data from the WOCE 'fast delivery' DAC and tidal constituents from Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales (LEGOS). Further copies of the CD-ROM are available from the WOCE Sea Level DACs.

The complete contents of the CD-ROM is as follows:

• WOCE 'Fast delivery' Sea Level Data Set: This section of the CD-ROM has been supplied by the UHSLC and contains in-situ sea level data from three projects. These are (1) the IGOSS Sea Level Program in the Pacific (ISLP-Pac), (2) the WOCE 'fast delivery' data set, and (3) the UHSLC Research Quality Data Set.
• WOCE 'Delayed-mode' Sea Level Data Set: This section of the CD-ROM contains the WOCE 'delayed-mode' sea level data set. In addition to the sea level data measured from coastal tide gauges, data from bottom pressure recorders are also included.
• Tidal Constants from the WOCE Sea Level Data Set: Tidal harmonic constants, confidence limits and power spectra have been produced from the WOCE Sea Level Data. These are available from both the 'Fast delivery' and the 'Delayed mode' sea level data sets. This has been contributed by Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales (LEGOS).
• PSMSL Monthly and Annual Mean Sea Level Data Set: This directory includes the contents of the PSMSL public directory as of December 1997.
• GLOSS Station Handbook (Preliminary Release of Version 4.0): This directory contains GLOSS Station Handbook Information Sheets from the preliminary release of Version 4.0 (February 1998) of the Handbook, a selection of maps and annual mean sea level plots.
• IOC Manuals and Guides No. 14: Volumes I and II: These two volumes comprise the IOC Manual on Sea Level Measurement and Interpretation. Volume I (Basic Principles) was published in 1985 and is based on training courses held at Bidston Observatory on behalf of PSMSL and IOC. It contains information on the scientific aspects of sea level change and on practical aspects of sea level measurement and data reduction. Volume II (Emerging Technologies) was published in 1994 and is complementary to the earlier volume, extending and updating the material on measurements.

Data are made available on the Web (or ftp) in addition to being distributed on CD-ROM. Requests for data are thus generally self-service, and have continued at a steady level. The WOCE Data Products Committee has set a timetable for production of Versions 2.0 and 3.0 of the WOCE Global Data Set on CD-ROM. The plan is for version 2.0 to be released in May 2000 and Version 3.0 in May 2002.

The WOCE 'Delayed-mode' Sea Level DAC is also responsible for the bottom pressure recorder data collected as part of WOCE. Related to this there have recently been efforts at POL to establish a global ocean bottom pressure database. GLOUP (Global Undersea Pressure) intends to provide easy access to the historical database of in-situ bottom pressure recorder data. There are currently 179 records available on-line; these are mostly in the North and South Atlantic, and the sector of the Southern Ocean. Almost all of the data presently available has been collected by POL, although it is intended that more data will be added as BODC and/or POL receive them.

Lesley Rickards
8th May 1999