Satellite Laser Ranging Reveals Ocean Mass as Key Driver of Sea-Level Rise

A research team from The Hong Kong Polytechnic University has, for the first time, used Satellite Laser Ranging (SLR) technology to generate precise global records of ocean mass changes spanning 1993 to 2022. Their findings, published in the Proceedings of the National Academy of Sciences (PNAS), confirm that the increase in ocean mass is the primary driver of global sea-level rise.

Global mean sea level has been rising at an average rate of about 3.3 millimeters per year, with acceleration observed in recent decades—an unmistakable sign of intensifying climate change. Sea-level rise is primarily caused by two factors: thermal expansion of seawater as it absorbs heat, and the addition of freshwater from melting ice on land, which increases ocean mass.

By developing innovative forward-modeling techniques, the team overcame long-standing limitations of conventional SLR in spatial resolution and coverage, enabling long-term monitoring of global ocean mass. Results show that over the past 30 years, sea level has risen by approximately 90 millimeters, with about 60% attributable to ocean mass increase. Since 2005, ocean mass growth has become the dominant contributor. Further analysis revealed that more than 80% of the additional mass comes from melting polar ice sheets and mountain glaciers, with accelerated ice loss from Greenland playing a particularly critical role.

This study represents the first direct observation-based quantification of global ocean mass change. It provides essential data for validating climate models and improving projections of future sea-level rise, while also establishing SLR as a vital tool for climate change research.