The study and monitoring of recent and present-day climate variations in sea level are organised on a world scale around the GLOSS programme of the Intergovernmental Oceanographic Commission of UNESCO. This programme relies on a network of around 300 coastal tide gauge stations (see above map) that are supplemented by denser regional networks. The GLOSS stations were recently organised around three poles of scientific interest:
> GLOSS-LTT, for the study of long term trends in sea level,
> GLOSS-ALT, for the "calibration" of satellite radar altimetres,
> GLOSS-OC, for the monitoring of general ocean circulation.
However, the scientific objectives may evolve. For instance, since the tsunami in Sumatra in December 2004 a fourth aspect, related to extreme events (tsunamis and storm waves), has been added to the GLOSS network applications, henceforth enhancing the stations technical requirements.
GLOSS Group of Experts
The group of experts is made up of national contacts, engineers and scientists. The mission entrusted to this group is to monitor the development of the programme and ensure that the scientific aims are matched by the financial support and technological advances. The scientific aims may also evolve as pointed out above.
"Best effort"
It should be noted that the IOC does not have the finances to build or maintain this kind of observation network. The success of the GLOSS programme depends on the volontary participation of countries and national bodies. It is indeed at the national level that concrete financial resources must be found. The IOC focuses on coordinating the resources and efforts of the participants on a world scale.
GLOSS Implementation Plan 2012
GLOSS data assembly center for GNSS stations (SONEL)
Tide gauge at Saint Jean-de-Luz
Since November 2011, the role of GLOSS data assembly center for GNSS (GPS) stations at or nearby tide gauges is played by SONEL. SONEL is supported by the University of La Rochelle and the French INSU/CNRS institute (the founding members are SHOM, IGN, LIENSs and LEGOS). It is the primary data center for the GPS Tide Gauge Benchmark Monitoring Pilot Project (TIGA) pilot project, which has turned into a permanent service of the International GNSS Service (IGS) in 2010.
SONEL provides information about the status of GNSS stations at or nearby tide gauges through a web-based monitoring facility (e.g., the above dynamic map). It assembles, archives, and distributes GNSS observation and metadata. In the next implementation plan (GIP 2012), GLOSS will continue to rely on TIGA (IGS) and SONEL for the assembling, processing and distribution of GNSS data at tide gauges. GLOSS will work with TIGA (IGS) to define the useful sea-level oriented products of GNSS analyses and its most appropriate standards and formats for distribution to the sea-level community, concise while informative and complete.
Key to this endeavor will be the maintenance of survey records linking the GNSS antenna to the tide gauge benchmark. Towards this aim, SONEL has started coordinating with the PSMSL to make this important metadata available for all GLOSS stations (Click on the image for further information).
All tide gauge operators, whether associated with GLOSS or not, are welcome to have their GNSS (GPS) data and metadata included in the SONEL data center facility for ensuring state-of-the-art processing (e.g., TIGA). GLOSS national contacts have the responsability to ensure that the GLOSS requirements are fullfilled at the stations for which the country has committted. The requirements include a GNSS antenna located as close to the gauge as possible (IOC Manuals & Guides, No. 14 (IV), pp. 52).
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