In a new study published today in the journal Sciencethe Cardiff University team was able to pinpoint exactly how the tilt and wobble of the Earth orbiting the Sun has influenced the melting of ice caps in the northern hemisphere over the past 2 million years about.
Scientists have long known that the rise and fall of massive Northern Hemisphere ice caps result from changes in the geometry of Earth’s orbit around the Sun.
Two aspects of the Earth’s geometry can influence the melting of ice caps: obliquity and precession.
Obliquity is the angle at which the Earth tilts as it moves around the Sun and is the reason why we have different seasons.
Precession is the way the Earth wobbles as it spins, much like a slightly off-center spinning top. The angle of this oscillation means that sometimes the northern hemisphere is closest to the Sun and other times the southern hemisphere is closest, which means that approximately every 10,000 years a hemisphere will have summers hotter than the other, before tipping over.
Scientists have determined that over the last or so million years, the combined effects of obliquity and precession on the waxing and decline of Northern Hemisphere ice sheets have resulted, through complex interactions within climate system, glacial cycles lasting about 100,000 years.
However, before 1 million years ago, in a period known as the Early Pleistocene, the length of glacial cycles was controlled only by obliquity and these glacial cycles lasted almost exactly 41,000 years.
For decades, scientists have puzzled over why precession didn’t play a bigger role in driving Ice Age cycles during this time.
In their new study, the Cardiff University team reveals new evidence suggesting that precession did indeed play a role in the early Pleistocene.
Their results show that more intense summers, driven by precession, have always caused the melting of the Northern Hemisphere ice sheets, but before 1 million years ago these events were less devastating and did not lead to melting. complete collapse of the ice caps.
The study’s lead author, Professor Stephen Barker, of Cardiff University’s School of Earth and Environmental Sciences, says “Early Pleistocene ice sheets in the northern hemisphere were smaller than their younger counterparts and restricted to higher latitudes where the effects of obliquity dominate over 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 major effort, involving more than 12 years of painstaking laboratory work to process almost 10,000 samples and the development of a range of new analytical approaches. an end to a long-standing problem in paleoclimatology and ultimately contribute to a better understanding of the Earth’s climate system.”
“Improving our understanding of Earth’s climate dynamics, even in the distant past, is crucial if we hope to predict changes over the next century and beyond. Ongoing changes may be man-made, but there is no There is only one climate system and we need to understand it.”
Earth’s orbit affects millennial climate variability
Stephen Barker et al, Persistent influence of precession on northern ice sheet variability since the early Pleistocene, Science (2022). DOI: 10.1126/science.abm4033. www.science.org/doi/10.1126/science.abm4033
Provided by Cardiff University
Quote: Scientists shed new light on role of Earth’s orbit in fate of ancient ice sheets (2022, May 26) Retrieved May 27, 2022 from https://phys.org/news/2022-05-scientists- role-earth-orbit-sort.html
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