Drifting Continents Caused the Quaternary Ice Age 2.6 Million Years Ago

What caused the ice age 2.6 million years ago? Scientists may have just answered that question. They've found out a major new theory that explains why an ice age covered large parts of the Northern Hemisphere.

Learning about past ice ages is no easy task, and relies largely on collecting mineral samples and using them as a type of environmental road map to the past. In this case, the researchers analyzed deposits of wind-blown dust called red clay that accumulated between six million and two and a half million years ago in north central China. They then used these samples to reconstruct changing monsoon precipitation and pressure.

"Until now, the cause of the Quaternary ice age had been a hotly debated topic," said Thomas Stevens, one of the researchers, in a news release. "Our findings suggest a significant link between ice sheet growth, the monsoon and the closing of the Panama Seaway, as North and South America drifted closer together. This provides us with a major new theory on the origins of the ice age, and ultimately our current climate system."

More specifically, the scientists found that the joining of North and South America changed the salinity of the Pacific Ocean. This, in turn, caused major ice sheet growth across the Northern Hemisphere since the change in salinity encouraged sea ice to form. The sea ice then changed wind patterns and lead to increased and intensified monsoons, which caused an increase in snowfall.

"This led us to discover a previously unknown interaction between plate tectonic movements in the Americas and dramatic changes in global temperature," said Stevens. "The intensified monsoons created a positive feedback cycle, promoting more global cooling, more sea ice and even stronger precipitation, culminating in the spread of huge glaciers across the Northern Hemisphere."

The findings are published in the journal Nature Scientific Reports.