The solar cycle’s hidden role in sea level variability
A new study identifies a recurring 11-year oscillation in global mean sea level linked to the solar cycle. The analysis shows that solar activity influences rainfall distribution and terrestrial water storage, leading to measurable shifts in sea level that align with peaks and troughs in the Sun’s natural cycle.
Image credit: NASA/ISS
New research points to a surprising link between the Sun’s 11-year cycle and short-term changes in global sea level. These shifts don’t come from ocean warming or melting ice. Instead, solar activity appears to shift global rainfall patterns, moving water between land and sea.
Led by Shuhei Masuda and colleagues, the research draws on over a century of climate records and two decades of satellite altimetry. It pinpoints a clear 11-year oscillation in the Global Mean Sea Level Trend (GMSLT), closely aligned with the solar cycle as tracked by sunspot numbers and galactic cosmic ray (GCR) fluxes.
The process largely hinges on how much water is stored on land, including in soil, rivers, and vegetation. During the peak of the Sun’s cycle, rainfall decreases in major regions like the Amazon, India, and Southeast Asia. This causes more water to flow into the ocean, raising sea levels. During the low point of the cycle, these areas get more rain, more water remains on land, and sea levels dip slightly.
The team estimates that the amplitude of the solar-driven GMSLT oscillation is about 1.3 mm (0.051 inches) per year, with corresponding shifts in land water storage matching closely in both timing and magnitude.
To trace the link, the researchers looked at the Palmer Drought Severity Index (PDSI) and satellite data on land water storage. Both showed steady 11-year swings linked to solar activity. The pattern is clearest when solar minimum lines up with the easterly phase of the Quasi-Biennial Oscillation (QBO), a regular wind shift near the equator.
Solar activity affects the Quasi-Biennial Oscillation, which then changes the strength of the tropical weather pattern of Madden-Julian Oscillation (MJO). When the MJO is stronger, it can impact how and when El Niño and La Niña events develop. These events shift rainfall around the world, moving water between land and ocean.
This sequence begins with the Sun and moves through the QBO, the MJO, El Niño and La Niña, and ends with land water storage. It connects changes in the Sun to real shifts in sea level. It also explains some 10-year patterns in sea level records. These patterns were once seen as random or blamed on natural climate swings.
About 10 percent of the world’s population lives in coastal areas less than 10 m (32.8 feet) above sea level. Small changes in how fast sea levels rise can change local flood risks and affect long-term planning.
Knowing how solar cycles influence water movement could improve forecasts from seasons to decades.
References:
1 Origin of the solar-cycle imprint on global sea level change – Shuhei Masuda, John Philip Matthews and Yosuke Alexandre Yamashiki – Scientific Reports – May 16, 2025 – DOI https://doi.org/10.1038/s41598-025-99880-2 – OPEN ACCESS
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