Scientists have finally put to bed a long-standing question about the role of Earth’s orbit in managing global cycles of the ice age.
In a new study published today in the journal Sciencea team from Cardiff University was able to pinpoint how the Earth’s tilt and oscillation in orbit around the Sun affected the melting of ice sheets in the Northern Hemisphere over the past 2 million years or so.
Scientists have long known that the increase and decrease of massive ice sheets of the Northern Hemisphere is due to changes in the geometry of the Earth’s orbit around the Sun.
There are two aspects of the Earth’s geometry that can affect the melting of ice sheets: tilt and precession.
Tilt is the angle of the Earth when moving around the Sun and is the reason that we have different seasons.
Precession is how the Earth oscillates in rotation, similar to rotating with a small point from the center. The angle of this fluctuation means that sometimes the Northern Hemisphere is closest to the Sun and other times the Southern Hemisphere, which means that about every 10,000 years in one hemisphere there will be warmer summers than others. before it changes.
Scientists have determined that over the past million years or so, the combined effects of tilt and precession on the rise and fall of the ice sheets of the Northern Hemisphere have led, through complex interactions within the climate system, to ice age cycles of about 100,000 years.
However, up to 1 million years ago, during the period known as the Early Pleistocene, the length of ice age cycles was controlled only by tilt, and these ice age cycles were almost equal to 41,000 years.
For decades, scientists have wondered why precession did not play a more important role in the movement of ice age cycles during this period.
In their new study, the Cardiff University team found new evidence that precession did play a role in the early Pleistocene.
Their results show that the more intense summer caused by the precession always caused the melting of the ice sheets of the Northern Hemisphere, but until 1 million years ago these events were less destructive and did not lead to the complete disintegration of the ice sheets.
Lead author Professor Stephen Barker of Cardiff University School of Earth and Environmental Sciences said: “Early Pleistocene ice sheets in the northern hemisphere were smaller than their recent counterparts and were limited to higher latitudes where tilt effects dominated explains why it took us so long to find evidence of precession in the early Pleistocene.
“These findings are the culmination of a major effort involving more than 12 years of painstaking work in the laboratory to process nearly 10,000 samples and develop a number of new analytical approaches. Thanks to this, we can finally stop a long time. paleoclimatology and ultimately contribute to a better understanding of the Earth’s climate system.
“Improving our understanding of the Earth’s climate dynamics, even in the distant past, is crucial if we hope to predict change in the next century and beyond. Current change can be made by man, but there is only one climate system and we need to understand it.”
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