Atmospheric composition and circulation over the tropical western Pacific Ocean play important roles in the Earth’s climate system. In this remote region, rising air heated by some of the warmest seawater in the world moves gases produced by ocean organisms and other chemicals to higher altitudes, where water vapor and ozone exert their strongest influence on the climate. As the climate warms, the intensity of this transport mechanism will increase and may contribute to large-scale changes in atmospheric composition. Details of these dynamics, including how they vary over time and space, are needed to accurately model the distribution of water vapor and ozone at high altitudes and to predict their impacts on climate. To address gaps in knowledge about these dynamics, an intensive field study using three research aircraft was conducted jointly by scientists from the United States and the United Kingdom, affiliated with the NSF-funded National Center for Atmospheric Research, NASA, NOAA, and several U.S. and European universities.

Analyses show that in addition to the role of local transport mechanisms, large-scale circulations also alter atmospheric composition over the Pacific, creating distinct structures in ozone and water vapor. Measurements also show that air over the remote, tropical-Pacific Ocean often contains significant amounts of pollutants associated with slash-and-burn agriculture in Asia and Africa. In addition, rising-air movement in the region was observed to transport chemicals produced by biological processes in the ocean to the upper atmosphere, where they contribute to ozone destruction.

These findings provide important new insight into how the remote, tropical-Pacific atmosphere interacts with and influences the distribution of ozone, water vapor, and other particles in the upper atmosphere. Follow-on research will examine how improved understanding of these transport processes can improve the ability to model upper-atmospheric composition and regional- and global-climate forcings.