Solar activity can manipulate deep-sea climate: study

BEIJING -- Solar activity not only affects temperatures on Earth's surface, but can also "control" climate change in the deep sea, according to a group of Chinese researchers.

Using eight decades of ocean reanalysis, they showed that the 11-year solar cycle robustly modulates the volume of a subsurface water mass in the North Pacific Ocean, the North Pacific Eastern Subtropical Mode Water (NPESTMW), said the researchers in an article published in the journal Geophysical Research Letters.

The NPESTMW, connecting the subtropics and tropics, forms at the ocean surface in winter and sinks, transferring heat and carbon to the deep ocean and influencing climate variability on timescales of years to decades.

Researchers at the Institute of Oceanology, Chinese Academy of Sciences (IOCAS), found that one to two years after the solar maximum, the formation of this mode of water was significantly suppressed.

The mechanism of this process is not as simple as solar heat directly warming the ocean, said Wang Jianing, a researcher at the IOCAS. During periods of high solar activity, anomalous cyclonic circulation over the formation region weakens surface winds and reduces ocean heat loss, suppressing winter mixed layer deepening and mode water formation.

However, the strength of this solar influence varies over time, according to the research article. A long-term natural climate fluctuation in the Atlantic Ocean further amplifies it, helping explain why the sun's imprint on climate has been particularly pronounced since the 1990s.

These findings reveal a new mechanism for incorporating solar activity, a predictable external forcing source, into decadal climate prediction.