(ORDO NEWS) — Scientists have finally put an end to the long-standing question about the role of the Earth’s orbit in the formation of global ice age cycles.
In a new study published in the journal Science, a team from Cardiff University has been able to determine exactly how the Earth’s tilt and wobble in its orbit around the Sun has affected the melting of ice sheets in the Northern Hemisphere over the past 2 million years.
Scientists have long known that the rise and fall of the massive ice sheets of the Northern Hemisphere is the result of changes in the geometry of the Earth’s orbit around the Sun.
There are two aspects of the Earth’s geometry that can influence the melting of ice sheets: tilt and precession.
The obliquity is the angle of the earth as it moves around the sun, which is why we have different seasons.
Precession is the wobble of the Earth as it rotates, like a slightly off center spinning top. The angle of this wobble means that sometimes the Northern Hemisphere is closest to the Sun and sometimes the Southern Hemisphere, meaning that about every 10,000 years one hemisphere will have a warmer summer than the other.
Scientists have determined that over the past million years, the combined influence of tilt and precession on the rise and fall of ice sheets in the Northern Hemisphere has resulted in ice age cycles of about 100,000 years, through complex interactions in the climate system.
However, until 1 million years ago, during a period known as the Early Pleistocene, the length of Ice Age cycles was only controlled by tilt, and these Ice Age cycles lasted almost exactly 41,000 years.
For decades, scientists have puzzled over why precession did not play a more important role in driving ice age cycles during this period.
In their new study, the Cardiff University team has found new evidence that precession did play a role in the early Pleistocene.
The results of the study show that more intense precession-driven summers have always caused the Northern Hemisphere ice sheets to melt, but until 1 million years ago, these events were less destructive and did not lead to the complete destruction of the ice sheets.
Study lead author Professor Stephen Barker, from the School of Earth and Environmental Sciences at Cardiff University, said: “Early Pleistocene ice sheets in the northern hemisphere were smaller than their later counterparts, and were limited to higher latitudes, where the influence of the inclined plane dominated the precession.
This, probably explains why it took us so long to find evidence of precessional forcing in the early Pleistocene.
“These results are the culmination of a great deal of work spanning over 12 years of painstaking work in the lab, processing almost 10,000 samples and developing a number of new analytical approaches.
With this, we can finally put an end to a long-standing problem in paleoclimatology and ultimately contribute to a better understanding the Earth’s climate system.
“Improving our understanding of Earth’s climate dynamics, even in the distant past, is critical if we hope to predict changes over the next century and beyond. Current changes may be man-made, but there is only one climate system and we must understand it.”
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