At a Glance
- Researchers created the first continuous 30-year record of global ocean mass change using satellite laser ranging, providing critical data from 1993 to 2022 for climate studies.
- Global mean sea level rose by approximately 90 millimeters over the three decades, with about 60% of this increase caused by the addition of water from melting land ice.
- The study found that melting land ice from Greenland and glaciers is the dominant contributor, accounting for over 80% of the total increase in global ocean mass.
- The rate of sea level rise is accelerating, primarily driven by the rapid increase in ocean mass resulting from climate warming and amplified ice loss, particularly since the 2000s.
- This new data successfully closes the sea level budget, as the sum of ocean warming and mass gain now matches the total sea level rise observed by satellites.
For the first time, researchers have utilized a traditional satellite technique to create a continuous 30-year record of the world’s ocean mass gain, revealing that melting land ice is the primary cause of modern sea level rise. A study by a team at The Hong Kong Polytechnic University, published in the Proceedings of the National Academy of Sciences, found that from 1993 to 2022, the global mean sea level rose by approximately 90 millimeters, with about 60% of that increase attributed to added water.
Global mean sea level (GMSL) rise, a key indicator of climate change, is driven by two main processes. The first is thermal expansion, where ocean water expands as it absorbs heat from a warming atmosphere. The second, known as barystatic sea level change, is the physical addition of water to the oceans, primarily due to the melting of glaciers and polar ice sheets. While satellite altimeters have tracked the total GMSL since 1993, directly measuring the added water mass has been difficult, as dedicated gravity-monitoring satellites like GRACE were not launched until 2002, leaving a critical decade-long gap in the data.
To fill this gap, the research team revived a decades-old technique called Satellite Laser Ranging (SLR). This method involves precisely measuring the distance to satellites by bouncing lasers off them from ground stations, which allows scientists to detect tiny changes in Earth’s gravity field caused by mass moving around the planet. Although SLR traditionally has a low spatial resolution, the team developed an innovative modeling approach that overcame this limitation, enabling them to produce a reliable, independent record of global ocean mass change that stretches back to 1993 and aligns remarkably well with newer satellite data.
The findings confirm that climate warming is accelerating ice loss, which in turn is causing sea levels to rise at a faster rate. Over the entire 30-year period, melting ice from polar sheets and mountain glaciers accounted for over 80% of the total increase in ocean mass. This new record helps “close” the sea level budget, meaning the measured rise in GMSL now matches the sum of its two components: thermal expansion and added water mass. This validation provides crucial data for improving climate models that project future sea level rise scenarios.
References
- Hong Kong Polytechnic University. (2025, September 1). Satellite laser ranging technique reveals 90 mm sea-level surge over past 30 years. Phys.Org; Hong Kong Polytechnic University. https://phys.org/news/2025-09-satellite-laser-ranging-technique-reveals.html
- Nie, Y., Chen, J., Xu, G., & Löcher, A. (2025). Barystatic sea level change observed by satellite gravimetry: 1993–2022. Proceedings of the National Academy of Sciences, 122(27), e2425248122. https://doi.org/10.1073/pnas.2425248122
