Atlantic Ocean temperatures during the Late Cretaceous Epoch 70 million years ago, which is an example of greenhouse climate on earth, could help scientists understand the consequences of modern increases in greenhouse gases.

A new research from the University of Missouri indicates that pre-historic greenhouse data from the ocean could help predict the Earth's future.

The findings of the study showed that at the end of the Late Cretaceous greenhouse interval, water sinking around Greenland was replaced by surface water flowing north from the South Atlantic. This change, which started about five million years before the asteroid impact that ended the Cretaceous Period, caused the North Atlantic to warm while the rest of the globe cooled.

"We are examining ocean conditions from several past greenhouse climate intervals so that we can understand better the interactions among the atmosphere, the oceans, the biosphere, and climate," said Kenneth MacLeod, professor of geological sciences in the College of Arts and Science.

"The Late Cretaceous Epoch is a textbook example of a greenhouse climate on earth, and we have evidence that a northern water mass expanded southwards while the climate was cooling. At the same time, a warm, salty water mass that had been present throughout the greenhouse interval disappeared from the tropical Atlantic."

MacLeod noted that while high atmospheric levels of carbon dioxide caused Late Cretaceous warmth, ocean circulation influenced how that warmth was distributed around the globe. In addition, ocean circulation patterns changed significantly as the climate warmed and cooled.

"Understanding the degree to which climate influences circulation and vice versa is important today because carbon dioxide levels are rapidly approaching levels most recently seen during ancient greenhouse times," said MacLeod.

"In just a few decades, humans are causing changes in the composition of the atmosphere that are as large as the changes that took millions of years to occur during geological climate cycles."

Sponsored by the National Science Foundation, the paper, "Changes in North Atlantic circulation at the end of the Cretaceous greenhouse interval," was published in the October online edition of the journal Nature Geoscience. Coauthors include C. Isaza Londoño of the University of Missouri; E.E. Martin and C. Basak of the University of Florida, and A. Jiménez Berrocoso of the Unviersity of Manchester, United Kingdom.