Last Updated on June 7, 2026 by Staff
When talking about rising sea levels scientists usually focus on two reasons: melting ice sheets and seawater getting warmer and expanding. New research says there’s another important factor that’s been mostly ignored.
A study in Geophysical Research Letters shows that Earth’s gravity, crust movement and small changes in the planet’s rotation can also affect sea-level rise. These hidden processes can make ocean levels change more near coastlines making future flooding risks bigger than many current projections say.
Researchers think this missing piece could help us understand how rising oceans will affect areas of the world.
The Hidden Force
As the climate gets warmer ocean currents and water density patterns change. This makes water move from one place to another redistributing mass around the planet.
The study says this movement causes what scientists call GRD effects. Gravity, Rotation and Deformation. These effects happen because Earth responds physically when large amounts of water gather in one place or disappear from another.
When ocean water gathers in an area the added mass increases local gravitational pull. At the time the weight slightly bends and deforms the Earth’s crust beneath it. Even the planet’s rotation can shift a bit as mass is redistributed.
These processes create sea-level changes that aren’t currently included in many standard climate projections.
Earth’s Response
Researchers describe Earth’s reaction to shifting ocean mass as a three-part process.
First, increased water mass makes local gravity stronger, pulling water toward that area and raising sea levels more. Second the weight of the water causes the Earth’s crust to flex and deform making the local sea level appear higher.
Third, the redistribution of mass slightly changes Earth’s balance. This tiny wobble affects how water spreads across the globe moving it toward areas where gravitational forces get stronger.
To study these effects scientists used climate models that projected changes in ocean mass through 2100. They then added GRD physics to their calculations.
The results showed that wherever water accumulates these hidden physical forces tend to make sea-level rise worse. Some deep-ocean areas may actually experience lower sea levels than previously predicted.
Coastal Impact
The study found that the effects aren’t spread equally around the globe.
Coastal areas with continental shelves and high-latitude locations seem to be the most vulnerable. Researchers estimate that by the end of the century some coastal areas could experience up to five centimeters of sea-level rise beyond what conventional projections say.
Five centimeters may seem small. It can have big consequences. Even a small increase in sea level can make storm surges stronger, worsen flooding and increase the frequency of high-tide flooding events.
The researchers also found that GRD effects account for 15% of the sea-level variability caused by dynamic ocean mass redistribution. This means some areas may face flood risks than expected if these effects are ignored.
Tropical coastlines, Arctic areas and parts of Southeast Asia may experience some of the impacts.
Planning Ahead
Although GRD effects are smaller than the impacts of melting glaciers or thermal expansion they’re still important for long-term planning.
Many cities, island nations and coastal communities rely on sea-level projections when designing flood defenses, infrastructure and adaptation strategies. If those projections underestimate sea levels communities may be less prepared for rising waters.
The researchers argue that future climate models should include gravity, rotation and deformation effects. This would give an accurate picture of regional flood risks and help policymakers make better decisions.
The study reminds us that Earth’s climate system is influenced by more than temperature. The planet’s own gravity, flexible crust and subtle rotational shifts can shape where ocean water ends up.
As global warming continues, understanding these hidden forces will become more important. Ignoring them could mean underestimating sea-level rise by around 15% leaving coastal regions more vulnerable than current forecasts suggest. By including these recognized processes, in future predictions scientists hope to provide communities with the information needed to better prepared for a changing world.