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Research Links Rainfall and Ocean Circulation in Past and Present

Researchers have found that changes in ocean currents in the Atlantic Ocean influence rainfall in the Western Hemisphere, and that it’s a system that has been linked for thousands of years.

Their findings, published on Jan. 26, 2018, in Nature Communications, provide a detailed look into Earth’s past climate and the factors that influenced it. The research could help scientists understand how these factors may influence our future climate.

“The mechanisms that seem to be driving this correlation [in the past] are the same that are at play in modern data as well,” said lead author Kaustubh Thirumalai, postdoctoral researcher at Brown University who conducted the research while earning his doctorate at the Jackson School of Geosciences.

The Atlantic Ocean surface circulation is an important part of the Earth’s global climate, moving warm water from the tropics towards the poles. The research tracked the changes in ocean circulation in new detail by studying three sediment cores extracted from the seafloor of the Gulf of Mexico in 2010. The samples give insight into factors that influenced the strength of the ocean current over 4,400 years in about 30-year increments.

The cores showed that, compared to today, the Atlantic Ocean surface circulation was much weaker during the Little Ice Age, a cool period that lasted from 1450-1850. Since these ocean currents are known to influence global climate, the researchers checked to see how they correlated with rainfall in the Western Hemisphere and how such a correlation could change over time.

Researchers compared the core data with proxies for precipitation data, such as data from tree rings and cave formations, as well as data
directly collected by humans during the last century on the temperature and salinity of the Gulf and rainfall in the Western Hemisphere. They also analyzed data from a climate model developed by the Max-Planck Institute for Meteorology in Germany