Extreme rainfall in eastern China linked to ocean warming

The equatorial Pacific is a key oceanographic region in the Earth’s climate system. According to a new study led by Rutgers University, warming of the upper ocean layers and stronger winds have been linked to increased rainfall in eastern China

Ocean heat content is a term that represents the amount of energy absorbed by seawater. Recent increases in ocean heat content have been implicated in the intensification of tropical storms – which draw their energy from the surface of the ocean. 

The link between ocean heating and rainfall on land is unclear. The Rutgers study, which is published in the journal Nature, provides new insight into this link.

“Our study suggests variations in ocean thermal structure affect the delivery of moisture, latent heat, and what happens when they arrive on land,” said Yair Rosenthal, professor at the Rutgers’ School of Art and Sciences and School of Environmental and Biological Sciences.

The latitudinal temperature gradient is the difference in sea-surface temperature between low and high latitudes. Temperature changes control how energy is absorbed by the equatorial upper ocean but also how wind carries moisture onto land.

The researchers found that over the past 360,000 years, there has been a correlation between monsoon rainfall in eastern China and the heat content of the Indo-Pacific Warm Pool. In this region, sea surface temperatures remain above 82°F year-round due to transport of moisture and latent heat absorbed in the water vapor from the ocean to the continent.  

The study revealed that changes in upper ocean heat respond to shifts in the Earth’s orbit that occur about every 23,000 years. This alters the distribution of solar radiation at each latitude.

By using two marine species – a surface dweller and an organism found 200 meters below the surface – the scientists reconstructed how the upper ocean thermal structure gets its heat and energy. The results were compared with climate model simulations and reconstructions of the monsoonal precipitation in eastern China.

The results have shown that the coupling of ocean heat content and monsoon variations is critical for regulating the global hydroclimate.

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By Katherine Bucko, Earth.com Staff Writer