Out of this world control on Ice Age cycles

Date:
May 15, 2023
Source:
National Institutes of Natural Sciences
Summary:
A research team, composed of climatologists and an astronomer, have
used an improved computer model to reproduce the cycle of ice ages
(glacial periods) 1.6 to 1.2 million years ago. The results show
that the glacial cycle was driven primarily by astronomical forces
in quite a different way than it works in the modern age. These
results will help us to better understand the past, present,
and future of ice sheets and the Earth's climate.


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FULL STORY ==========================================================================
A research team, composed of climatologists and an astronomer, have
used an improved computer model to reproduce the cycle of ice ages
(glacial periods) 1.6 to 1.2 million years ago. The results show that
the glacial cycle was driven primarily by astronomical forces in quite
a different way than it works in the modern age. These results will help
us to better understand the past, present, and future of ice sheets and
the Earth's climate.

Earth's orbit around the Sun and its spin axis orientation change
slowly over time, due to the pull of gravity from the Sun, the Moon,
and other planets.

These astronomical forces affect the environment on Earth due to changes
in the distribution of sunlight and the contrast between the seasons. In particular, ice sheets are sensitive to these external forces resulting
in a cycle between glacial and interglacial periods.

The present-day glacial-interglacial cycle has a period of about 100,000
years.

However, the glacial cycle in the early Pleistocene (about 800,000 years
ago) switched more rapidly, with a cycle of about 40,000 years. It has
been believed that astronomical external forces are responsible for this change, but the details of the mechanism have not been understood. In
recent years, it has become possible to investigate in more detail the
role of astronomical forces through the refinement of geological data
and the development of theoretical research.

A team led by Yasuto Watanabe at the University of Tokyo focused on
the early Pleistocene Epoch from 1.6 to 1.2 million years ago using an
improved climate computer model. Astronomical forces based on modern state-of-the-art theory are considered in these simulations. The large numerical simulations in this study reproduce well the glacial cycle
of 40,000-year of the early Pleistocene as indicated by the geological
record data.

From analysis of these simulation results, the team has identified three
facts about the mechanisms by which astronomical forces caused changes
in climate in those times. (1) The glacial cycle is determined by small differences in the amplitude of variation of the spin axis orientation
and the orbit of the Earth.

(2) The timing of deglaciation is determined mainly by the position of
the summer solstice on its orbit, which is at perihelion, not only by
the effect of periodical change of the tilt of the Earth's axis. (3)
The timing of the change in the spin axis orientation and the position
of the summer solstice on its orbit determines the duration of the
interglacial period.

"As geological evidence from older times comes to light, it is
becoming clear that the Earth had a different climatic regime than
it does today. We must have a different understanding of the role of astronomical forcing in the distant past," says Takashi Ito from the
National Astronomical Observatory of Japan, a member of this research team
who led the discussion on astronomical external forces. "The numerical simulations performed in this study not only reproduce the Pleistocene glacial-interglacial cycle well, but also successfully explain the
complex effects of how astronomical forcing drove the cycle at that time.

We can regard this work as a starting point for the study of glacial
cycles beyond the present day Earth."
* RELATED_TOPICS
o Earth_&_Climate
# Earth_Science # Ice_Ages # Climate # Geochemistry
o Fossils_&_Ruins
# Early_Climate # Fossils # Origin_of_Life # Evolution
* RELATED_TERMS
o Ice_age o Ice_sheet o Global_climate_model
o Greenland_ice_sheet o Mammoth o
Antarctic_ice_sheet o Geologic_temperature_record o
Temperature_record_of_the_past_1000_years

========================================================================== Story Source: Materials provided by
National_Institutes_of_Natural_Sciences. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Yasuto Watanabe, Ayako Abe-Ouchi, Fuyuki Saito, Kanon Kino, Ryouta
O'ishi, Takashi Ito, Kenji Kawamura, Wing-Le Chan. Astronomical
forcing shaped the timing of early Pleistocene glacial
cycles. Communications Earth & Environment, 2023; 4 (1) DOI:
10.1038/s43247-023-00765-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230515132024.htm

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