New way to estimate global rainfall and track ocean pollution

By measuring Beryllium-7 (⁷Be) isotope concentrations in the ocean, which is found naturally throughout Earth's atmosphere, Rosenstiel School scientists David Kadko and Joseph Prospero were able to provide a method to accurately estimate rainfall in remote regions of the ocean. The two-year study measured ⁷Be deposited in rain collectors at two sites in Bermuda and compared these estimates to those observed in the nearby Sargasso Sea.

"Over vast areas of the oceans the only rainfall data available are those made by using conventional rain collectors placed on islands," said Prospero, professor of marine and atmospheric chemistry at the UM Rosenstiel School. "However, rainfall on the island is not necessarily representative of that which falls in the surrounding ocean. Our paper shows that properly placed rain collectors on Bermuda do yield rainfall rates that agree with those determined through the ⁷Be measurements."

Rainfall is a major pathway by which man-made airborne pollutants and other naturally occurring chemicals enter the oceans. Berrylium-7, like man-made pollutants and other naturally occurring chemicals, attaches itself to atmospheric dust particles and enters the ocean during rain events. By understanding this process, scientists can establish new ways to quantify airborne pollutants deposited to the ocean.

"The accumulation of ⁷Be in the upper ocean provides a means of assessing ⁷Be deposition to the ocean on regional and global scales," said Kadko, professor marine and atmospheric chemistry of at the Rosenstiel and lead author of the study. "This then can be used to assess the deposition of other chemical species."