Global Sea Level Observing System (GLOSS)

GLOSS is the Global Sea Level Observing System, established by the IOC of UNESCO in 1985 to coordinate a high-quality global tide-gauge network. Its backbone is the GLOSS Core Network (GCN), about 290 stations distributed roughly evenly along the world’s coasts to sample sea-level variability for climate, tsunami warning, and altimeter calibration. GLOSS sets the data standards: the millimeter-accuracy target, the demand for a co-located GNSS station to monitor land movement, and delivery to PSMSL for the archived monthly means. More than 2,000 national stations now contribute beyond the core, with the operational subset feeding the IOC sea-level monitoring service in near real time.