Solar activity influences deep-sea climate, study shows

By the Editorial Team · Thursday, September 17, 2026

Chinese researchers have discovered that the 11-year solar cycle influences the volume of subsurface mode water in the North Pacific by altering atmospheric circulation and ocean heat loss. This finding reveals a new way solar activity affects deep ocean processes and suggests that including solar cycles in climate models could enhance the prediction of long-term climate variability.

A study conducted by Chinese researchers has found evidence that solar activity influences not only Earth's surface temperatures but also climate conditions in the deep ocean. Analyzing eight decades of ocean reanalysis data, the team identified a clear modulation of the North Pacific Eastern Subtropical Mode Water (NPESTMW) volume by the 11-year solar cycle.

The NPESTMW is a subsurface water mass that forms at the ocean surface during winter in the North Pacific. It plays a critical role in connecting subtropical and tropical regions by sinking and transporting heat and carbon into the deeper ocean, thereby affecting climate variability over periods ranging from years to decades.

Researchers at the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), reported in the journal Geophysical Research Letters that the formation of this mode water decreases significantly one to two years after the peak of solar activity, known as the solar maximum. According to Wang Jianing, a scientist involved in the study, this process is not simply the result of increased solar radiation directly warming the ocean. Instead, during times of heightened solar activity, stronger cyclonic atmospheric circulation above the NPESTMW formation region leads to weaker surface winds, which in turn reduce ocean heat loss. This chain of events suppresses the deepening of the winter mixed layer and limits the formation of the mode water.

The research also points out that the solar modulation of the NPESTMW varies over time. A longer-term natural climate oscillation in the Atlantic Ocean appears to amplify the solar effect, which may explain why the influence of solar activity on climate has been particularly noticeable since the 1990s.

Overall, these findings highlight a previously underappreciated mechanism by which predictable solar cycles can impact deep ocean processes and contribute to decadal-scale climate variability. The authors suggest that incorporating solar activity into climate models could improve the accuracy of future climate predictions.

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