Glaciers and Rising Seas: How Ice Loss Is Reshaping the World's Coastlines

Every tonne of glacier ice that melts adds water to the world's oceans. The mathematics is straightforward: the combined volume of the world's glaciers, ice caps, and ice sheets contains enough water to raise global sea levels by approximately 65 metres. While full melting is not a near-term prospect, even a fraction of that potential is transformative for the world's coastlines. Glacier melt — from mountain glaciers, ice caps, and the margins of the Greenland and Antarctic ice sheets — is currently the largest single contributor to observed sea level rise.

Measuring the Contribution

Scientists quantify glacier contributions to sea level rise using a combination of satellite gravimetry (measuring changes in Earth's gravitational field caused by ice mass loss), satellite altimetry (measuring changes in ice surface elevation), and mass balance modelling. The NASA satellite altimetry record shows that global mean sea level has risen by approximately 10 centimetres since 1993 — with ice melt from glaciers and ice sheets contributing roughly half of that rise, and thermal expansion of warming ocean water contributing the remainder.

Who Is Most at Risk

The communities most vulnerable to glacier-driven sea level rise are those in low-lying coastal areas — particularly small island developing states, river deltas, and heavily populated coastal megacities. The Maldives, Tuvalu, Kiribati, and Marshall Islands face existential risk from even moderate sea level rise. River deltas including the Ganges-Brahmaputra, Mekong, and Nile support hundreds of millions of people at elevations of only metres above current sea level. Coastal megacities including Miami, Mumbai, Shanghai, Bangkok, and Jakarta face enormous economic exposure to increased flooding frequency.