What is GLOSS?

The Global Sea Level Observing System (GLOSS) is an international programme conducted under the auspices of the Joint Technical Commission for Oceanography and Marine Meteorology (JCOMM) of the World Meteorological Organisation (WMO) and the Intergovernmental Oceanographic Commission (IOC). GLOSS aims at the establishment of high quality global and regional sea level 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 GLOSS10.

GLOSS Core Network defined by GLOSS10

Map showing GLOSS core network defined by GLOSS10

(Click on image to download a larger .pdf version)

The Core Network is designed to provide an approximately evenly-distributed sampling of global coastal sea level variations. Another component is the GLOSS Long Term Trends (LTT) set of gauge sites (some, but not all, of which are in the GCN) for monitoring long term trends and accelerations in global sea level. These will be priority sites for Global Positioning System (GPS) receiver installations to monitor vertical land movements, and their data will contribute to long term climate change studies such as those of the WMO-UNEP Intergovernmental Panel on Climate Change (IPCC).

The GLOSS altimeter calibration (ALT) set consists mostly of island stations, and will provide an ongoing facility for mission intercalibrations. A GLOSS ocean circulation (OC) set, including in particular gauge pairs at straits and in polar area, complements altimetric coverage of the open deep ocean within programmes such as the World Ocean Circulation Experiment (WOCE) and Climate Variability and Predictability (CLIVAR).

GLOSS can be considered a component of IOC's Global Ocean Observing System (GOOS), and particularly as a major contributor to its Climate and Coastal Modules. Information on the links between GLOSS and other IOC activities can be obtained from the IOC's web site.