Global sea level is not rising at a steady pace. While it is often represented as a smooth and gradual increase in records, new findings suggest something far more dynamic. Between 2010 and 2012, the rate of sea-level rise jumped from 2.9 to 4.1 millimetres per year – a 40% increase, which adds an extra annual volume equivalent to nearly 4,880 Lake Genevas.
This finding comes from a new study using satellite altimetry data, which challenges the prevailing view that sea levels rise gradually over time. The study analysed 30 years of satellite altimetry data from TOPEX/Poseidon and Jason missions, available through the Copernicus Climate Change Service. An international team led by geophysicist Anny Cazenave, scientific lead of ESA's Climate Change Initiative Sea Level project, conducted the analysis. The research is published in the journal Communications Earth & Environment.
Land water loss emerges as key driver of sea level surge
Acceleration of sea level early in the 2010s was not primarily driven by melting ice sheets or glaciers, according to the authors. Neither showed a significant shift in their melting rates during this period. Instead, they find evidence to suggest ocean thermal expansion and changes in terrestrial water storage were primarily responsible for the shift.
Ocean thermal expansion describes how seawater expands in volume as it warms up, while terrestrial water storage changes refer to net shifts in water from land – from lakes, rivers, soil and groundwater – to the ocean. Ocean mass data from the Sea Level Budget Closure project, combined with GRACE satellite observations, enabled the research team to trace how these two processes caused the acceleration.
Climate cycles drove water redistribution
The authors suggest that this redistribution of water is mainly attributed to natural climate phenomena. The Pacific Decadal Oscillation, which drives shifts in ocean temperature, and the North Atlantic Oscillation, which affects atmospheric circulation and precipitation, are cited as the main drivers. Around 2012, both cycles shifted in a way that intensified water movement from land to ocean, indirectly amplifying sea level rise. Other recent studies have reported similar abrupt changes in precipitation, ocean temperatures and atmospheric circulation around the same time, suggesting that the climate system adjusted dynamically in response to internal variability during the early 2010s.
“Natural climate variability can cause fluctuations in sea level ranging from annual to decades-long, in addition to the rise in sea we are seeing from human-caused climate change. Our study shows that the rate of global mean sea level increased abruptly around 2012. Because other studies have also seen rapid changes in other climate variables around this time, we wonder if we are seeing a regime shift. The key research question now is whether this shift will be sustained”, says Sarah Connors, scientist of the Climate Office of the European Space Agency and Co-author of the study.
The power of long-term satellite records
Effective adaptation to sea level rise depends on reliable predictions of when and why abrupt shifts occur – predictions that require robust datasets and integrated observations. This study demonstrates the power of such an approach. Altimetry data from missions like TOPEX/Poseidon and Jason – which are being extended by Copernicus Sentinel-6 D – together with ocean mass data from ESA's Climate Change Initiative, revealed changes that would otherwise have gone unnoticed.
The use of multiple trend-change detection methods and tools like Bayesian Estimator of Abrupt Change, Seasonal and Trend, called BEAST, were critical in identifying these abrupt changes in global sea-level patterns with high accuracy. Such advanced methodologies helped confirm the connection between land-water loss, warming oceans, and the accelerated 40% rise observed during the early 2010s, demonstrating the true power of integrated, long-term observational records.
“Our analysis tells us that sea level change is more dynamic than previously assumed," says Anny Cazenave. "These sudden accelerations reveal limitations in traditional risk models and underscore the need for better observational data to inform infrastructure planning and climate adaptation strategies. Unpredictable regime changes in our climate pose significant challenges, and particularly for vulnerable coastal regions as far as sea level is concerned.”
Through integrated observations, scientists are better equipped to identify and explain the underlying processes driving environmental change and offer critical insights for climate adaptation strategies.
Read the full paper in Communications Earth & Environment: Abrupt trend change in global mean sea level and its components in the early 2010s | Communications Earth & Environment