The Amazon rainforest and the Sahara desert are an ocean apart, but researchers from this university and NASA’s Goddard Space Flight Center have found that the two environments are closely connected.

By analyzing seven years of data collected by NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite, the team found that about 22,000 tons of Saharan dust is deposited in Amazonian soil every year. That’s about the same amount the Amazon loses through floods and rains annually, according to the study.

The team’s research was published in the journal Geophysical Research Letters on Feb. 24.

“The fertilizing role of dust in [the] Amazon rainforest has been recognized before, however it remains poorly quantified and some confusion and ambiguity exists,” Hongbin Yu, a NASA research scientist at this university’s Earth System Science Interdisciplinary Center and the project’s lead author, wrote in an email.

The researchers found that as the dust travels across the Atlantic Ocean, it transports fertilizing phosphorus to the Amazon, replenishing the soil with the important nutrient and rendering the Amazon dependent on the Sahara.

“The long-distance transport of dust and nutrients from Africa to Amazonia is a beautiful example of what scientists refer to as the ‘Earth System,’” Doug Morton, a physical scientist at the Goddard Space Flight Center and a university professor, wrote in an email. “The connections that link the atmosphere, ocean, and land surface are fascinating. And, some of our greatest recent advances in Earth science have been to understand these long-distance connections using satellite data and computer models.”

The team focused on samples from the Bodélé Depression on the Sahara’s fringe and samples from Barbados and Miami to quantify the amount of phosphorus transported to the Amazon every year. The depression was once a lake bed, and it is rich in deposits of dead microorganisms that contain phosphorous.

“Previous studies have identified Africa as a likely source of new phosphorous inputs for Amazon forests based on the chemical composition of dust on both continents,” Morton wrote.

The researchers also found that the pattern of dust transported varies significantly. Between a high in 2007 and a low 2011, there was an 86 percent change in the amount of dust deposited.

While this statistic indicates that trends cannot be predicted yet, it also gives Yu and his colleagues the chance to speculate. Though the variation could be the result of high rainfall and less soil exposed to wind erosion on the southern border of the Sahara, the researchers believe the wind circulation patterns sweeping the dust into the atmosphere could also be a cause.

“Wind circulations change with season,” Yu wrote. “In northern hemispheric winter and spring, the inter tropical convergence zone (ITCZ, with strong precipitation) stays in the southern hemisphere. So dust is not fully removed along the path and a portion of dust can reach the Amazon. However, in summer and fall, ITCZ moves northward and hence dust plumes [move] northward. Most of dust can’t reach the Amazon.”

Internationally, the study is important to scientists’ understanding of dust’s role in an ecosystem and local and global climate, Morton wrote.

“Scientists around the world are working to understand how climate change will impact both human and natural systems,” Morton wrote. “Yet, climate change may also alter how water and nutrients are transported from Africa to Amazonia. Strengthening or weakening these connections in the Earth system could offset or accelerate some of the impacts from climate change.”