What is GLOSS?

The Global Sea Level Observing System (GLOSS) is an international sea level monitoring program designed to produce high-quality in situ sea level observations to support a broad research and operational user base. GLOSS was established by the UNESCO Intergovernmental Oceanographic Commission (IOC) in 1985 and it is currently formed by over 90 nations across the globe.

GLOSS provides oversight and coordination for global and regional sea level networks, and relies on feedback and direction from local tide gauge operators to maintain the creation of high-quality sea level observations. The climate, coastal and operational service modules of GLOSS contribute to the Global Ocean Observing System (GOOS), through the progressive development of the sea level measurement network, data exchange and collection systems, and preparation of sea level products for various user groups.

GLOSS remains under the auspices of the IOC and is one of the observing components under the World Meteorological Organization (WMO)/ IOC Joint Technical Commission for Oceanography and Marine Meteorology (JCOMM). 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 voluntary 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 global scale.

For a complete description of the GLOSS program, see the latest GLOSS Implementation Plan [pdf].

Why monitor sea level?

Tide gauge observations provide information on a wide spectrum of oceanographic processes, ranging from surface and internal tides to surface currents and ocean eddies. In situ observations of sea level are also needed to monitor and understand global sea level rise, as well as inter-annual to decadal sea level variations, which provide insight into ocean circulation changes on climate time scales. In addition, sea level observations are used to examine extreme events associated with tsunamis, storm surges, and other factors leading to short-term coastal inundation. Find out more about the scientific and practical applications of sea level information.

Given the multi-dimensional, multi-purpose nature of tide gauge observations, there is considerable benefit to be gained from well-designed sea level observing networks that support a broad research and operational user base. GLOSS was established to provide this range of services, and provide oversight and coordination for global and regional sea level networks in support of, and with direction from, the oceanographic and climate research communities.