Every summer millions of birds flock to the Arctic, and every summer an abnormal amount of cloud particles form in the atmosphere over the same region. These two events are more closely related than they appear, with new research tying them together via the thick layer of bird poop that coats much of the local landscape.

The discovery stems from research carried out over two years by an international team of scientists, who collected air samples for study over the Canadian Arctic. The team found that in the warmer months of the year, there was a big uptick in ammonia levels. The initial assumption was that this was coming from the sea, but the team soon ruled out this possibility with further investigation.

This lead them to suspect that the massive flock of birds that travel to the region had something to do with it, so they used calculations and computer modeling to explore this possibility. They found that as the excrement was broken down by bacteria, an amount of ammonia was released into the air which seemed to correspond with the sharp rise they noticed in their previous analysis.

When this ammonia blends with the sulfuric acid and water molecules that arise from the ocean spray, it forms airborne particles that head up into the atmosphere and promote cloud formation. And one of the effects of extra cloud formation, is the extra reflection of sunlight back into space, thus cooling the area. The researchers calculate that the cooling effect could exceed 1 W per meter squared near the biggest bird colonies.

"This newly identified and fascinating ecological-atmospheric connection highlights the interconnectedness of the many components of Earth's climate system," said Jeff Pierce, Associate Professor of Atmospheric Science at Colorado State University.

The research was published in the journal Nature Communications.