Global Sea Level Observing System (GLOSS)

Location of tide gauge at Lerwick
Location of tide gauge at Lerwick ©

What is GLOSS?

The Global Sea Level Observing System (GLOSS) is an international programme aiming to establish high quality global and regional sea level measurement networks for application to climate, oceanographic and coastal sea level research. The programme became known as GLOSS as it provides data for deriving the 'Global Level of the Sea Surface'.

The main component of GLOSS is the 'Global Core Network' (GCN) of 290 sea level stations around the world for long-term climate change and oceanographic sea level monitoring. The present definition of the GCN (the definition is modified every few years) is called GLOSS02.

GLOSS is conducted under the auspices of the Joint WMO/IOC Commission for Oceanography and Marine Meteorology (JCOMM) of the World Meteorological Organization (WMO) and the Intergovernmental Oceanographic Commission (IOC).

BODC’s role in GLOSS

BODC is responsible for maintaining the GLOSS Station Handbook, which was constructed in order to provide further information on each of the tide gauges in the GCN. Site maps are available for many of the stations. Plots of annual mean sea level are available for most sites.

There are links to the hourly values of sea level data held at the 'Fast-Delivery' Data Assembly Centre (latency less than one month) and the Joint Archive for Sea Level Data (JASL). Both are operated by the University of Hawai`i Sea Level Center (UHSLC). The 'Delayed-mode' Data Assembly Centre, where high frequency data are stored, is operated by BODC. Other sea level data held by these sites can be found by visiting their web pages. The Handbook also includes references to individual countries and organisations that have made their sea level data (hourly values) available on the web or have provided information about their tide gauge networks and how to obtain the data.

Sea level archaeology

In 1999 the GLOSS Group of Experts discussed the need for data archaeology of historic sea level records in order to possibly extend existing time series and/or gain access to observations that are not in digital form. A letter was circulated to the GLOSS contact list and to the International Oceanographic Data and Information Exchange (IODE) address list in August 2001. The letter requested all countries' tide gauge operators to assess their holdings of historical tide gauge data that can potentially be rescued.

Replies were received from over 20 countries and the results will be summarised and made available on the GLOSS web site.