New Evidence Suggests Panama Isthmus Older than Thought. Paleo Climate Implications.
April 29, 2015
Above, from BBC’s “Earth a Biography” – ideas about Atlantic circulation and it’s role in planetary glaciation may have to be rethought in light of new evidence that the Isthmus of Panama is older than previously believed.
The joining of the North and South American, it has been believed, was a critical influence on ocean circulation, that, combined with the gradual lowering of greenhouse gases in the atmosphere over the last 50 million years, lead to our current cycle of glacial and interglacial periods, timed by changes in the earth’s orbit and axial tilt, (Milankuvitch forces).
(Phys.org)—A team of researchers with members from Panama, Sweden, Switzerland and the U.S. has found evidence that suggests the Isthmus of Panama was formed much earlier than has been thought by most in the research community. In their paper published in Proceedings of the National Academy of Sciences, the team describes how they undertook a detailed study of fossil and molecular data of both terrestrial and marine life to create a better picture of the way the Isthmus came to be.
Conventional theory has placed the formation of the Isthmus of Panama at approximately 3.5 million years ago, connecting the North and South American continents. That event marked a major evolutionary occurrence for the planet as it allowed plants and animals to cross between the two continents, while simultaneously cutting off marine life that once passed between them—it also had a major impact on worldwide weather as the water flow between the Caribbean Sea and the Pacific Ocean was stopped. In this new effort, the researchers report that they have found evidence that shows the Isthmus was formed in a stop-and-go manner that began as far back as 20 million years ago.
To come to this conclusion, the team looked at fossil and molecular data collected from specimens found on both ends of the Isthmus as well as specimens that came from the sea. They claim their analysis shows that migrations between the two continents started much earlier than has been thought and that there were periods where such migrations were halted which meant the Isthmus had been covered over by water for a time, again, before rising to finally form the land mass we have today. Species passed between, the two continents, they report, at a reasonably steady pace, up until approximately six million years ago—at that point, the migration picked up in very noticeable ways.
The team plans to continue their research, looking for answers to such questions as to why it appears mammals took so much longer to migrate between the two continents than did other organisms. They also believe that because many modern models used to predict future climate change are based on assumptions from the past that include the Isthmus forming much more recently than it really did, some changes are going to have to be made to them.
Below, my recent vid on newest findings about a slowdown in Atlantic Circulation – “Nasty Surprise in the Greenhouse”.