From the University of Southern Denmark and the department of natural variation comes this study saying what we’ve all known for years.
Same forces as today caused climate changes 1.4 billion years ago
Natural forces have always caused the climate on Earth to fluctuate. Now researchers have found geological evidence that some of the same forces as today were at play 1.4 billion years ago.
Fluctuating climate is a hallmark of Earth, and the present greenhouse effect is by far the only force affecting today’s climate. On a larger scale the Earth’s climate is also strongly affected by how the Earth orbits around the sun; this is called orbital forcing of climate change. These changes happen over thousands of years and they bring ice ages and warming periods.
Now researchers from University of Southern Denmark, China National Petroleum Corporation and others have looked deep into Earth’s history and can reveal that orbital forcing of climate change contributed to shaping the Earth’s climate 1.4 billion years ago.
“This study helps us understand how past climate changes have affected Earth geologically and biologically”, says Donald Canfield, principal investigator and professor at Nordic Center for Earth Evolution, University of Southern Denmark.
The evidence comes from analyses of sedimentary records from the approximately 1.4 billion-year-old and exceptionally well preserved Xiamaling Formation in China.
Changes in wind patterns and ocean circulations
The sediments in the Xiamaling Formation have preserved evidence of repeated climate fluctuations, reflecting apparent changes in wind patterns and ocean circulation that indicates orbital forcing of climate change.
Today Earth is affected by fluctuations called the Milankovich cycles. There are three different Milankovich cycles, and they occur each 20,000, 40,000 and 100,000 years. Over the last one million years these cycles have caused ice ages every 100,000 years, and right now we are in the middle of a warming period that has so far lasted 11,000 years.
“Earth’s climate history is complex. With this research we can show that cycles like the Milankovich cycles were at play 1.4 billion years ago – a period, we know only very little about”, says Donald Canfield, adding:
“This research will also help us understand how Milankovitch cyclicity ultimately controls climate change on Earth.”
In the new scientific paper in the journal PNAS, the researchers report both geochemical and sedimentological evidence for repeated, short-term climate fluctuations 1.4 billion years ago. For example the fossilized sediments show how layers of organic material differed over time, indicating cycle changes in wind patterns, rain fall and ocean circulations.
“These cycles were a little different than today’s Milankovich cycles. They occurred every 12-16,000 years, 20-30,000 years and every 100,000 years. They were a little shorter – probably because the Moon was closer to Earth 1.4 billion years ago”, explains Donald Canfield.
Ref PNAS: Orbital forcing of climate 1.4 billion years ago Shuichang Zhanga, Xiaomei Wanga, Emma U. Hammarlundb, Huajian Wanga, M. Mafalda Costac, Christian J. Bjerrumd, James N. Connellyc, Baomin Zhanga, Lizeng Biane, and Donald E. Canfieldb.
Fluctuating climate is a hallmark of Earth. As one transcends deep into Earth time, however, both the evidence for and the causes of climate change become difficult to establish. We report geochemical and sedimentological evidence for repeated, short-term climate fluctuations from the exceptionally well-preserved ∼1.4-billion-year-old Xiamaling Formation of the North China Craton. We observe two patterns of climate fluctuations: On long time scales, over what amounts to tens of millions of years, sediments of the Xiamaling Formation record changes in geochemistry consistent with long-term changes in the location of the Xiamaling relative to the position of the Intertropical Convergence Zone. On shorter time scales, and within a precisely calibrated stratigraphic framework, cyclicity in sediment geochemical dynamics is consistent with orbital control. In particular, sediment geochemical fluctuations reflect what appear to be orbitally forced changes in wind patterns and ocean circulation as they influenced rates of organic carbon flux, trace metal accumulation, and the source of detrital particles to the sediment.
There is a wealth of evidence pointing to dramatic short-term climate change on Earth over the last few million years. Much of this climate change is driven by variations of Earth’s orbit around the Sun with characteristic frequencies known as Milankovitch cycles. Robust evidence for orbitally driven climate change, however, becomes rare as one descends deep into Earth time. We studied an exceptional record of climate change as recorded in 1.4-billion-year-old marine sediments from North China. This record documents regular changes in subtropical/tropical Hadley Cell dynamics. These changes in dynamics controlled wind strength, rainfall, and ocean circulation, translated into cyclic variations in sediment geochemistry, much like the orbital control on climate today and in the recent past.