Why does our planet experience an ice age every 100,000 years?

Earth
A composite image of the Western hemisphere of the Earth. Credit: NASA

Experts from Cardiff University have offered up an explanation as to why our planet began to move in and out of ice ages every 100,000 years.

This mysterious phenomena, dubbed the '100,000 year problem', has been occurring for the past million years or so and leads to vast ice sheets covering North America, Europe and Asia. Up until now, scientists have been unable to explain why this happens.

Our planet's ice ages used to occur at intervals of every 40,000 years, which made sense to scientists as the Earth's seasons vary in a predictable way, with colder summers occurring at these intervals.

However there was a point, about a million years ago, called the 'Mid-Pleistocene Transition', in which the ice age intervals changed from every 40,000 years to every 100,000 years.

New research published today in the journal Geology has suggested the oceans may be responsible for this change, specifically in the way that they suck (CO2) out of the atmosphere.

By studying the chemical make-up of tiny fossils on the , the team discovered that there was more CO2 stored in the deep ocean during the ice age periods at regular intervals every 100,000 years.

This suggests that extra carbon dioxide was being pulled from the atmosphere and into the oceans at this time, subsequently lowering the temperature on Earth and enabling vast ice sheets to engulf the Northern Hemisphere.

Lead author of the research Professor Carrie Lear, from the School of Earth and Ocean Sciences, said: "We can think of the oceans as inhaling and exhaling carbon dioxide, so when the ice sheets are larger, the oceans have inhaled carbon dioxide from the atmosphere, making the planet colder. When the ice sheets are small, the oceans have exhaled carbon dioxide, so there is more in the atmosphere which makes the planet warmer.

"By looking at the fossils of tiny creatures on the ocean floor, we showed that when ice sheets were advancing and retreating every 100,000 years the oceans were inhaling more carbon dioxide in the cold periods, suggesting that there was less left in the atmosphere."

Marine algae play a key role in removing CO2 from the atmosphere as it is an essential ingredient of photosynthesis.

CO2 is put back into the when water rises to the surface through a process called upwelling, but when a vast amount of sea ice is present this prevents the CO2 from being exhaled, which could make the ice sheets bigger and prolong the ice age.

"If we think of the oceans inhaling and exhaling carbon dioxide, the presence of vast amounts of ice is like a giant gobstopper. It's like a lid on the surface of the ," Prof Lear continued.

The Earth's climate is currently in a warm spell between glacial periods. The last ice age ended about 11,000 years ago. Since then, temperatures and sea levels have risen, and ice caps have retreated back to the poles. In addition to these natural cycles, manmade carbon emissions are also having an effect by warming the climate.


Explore further

Climate change likely to increase black carbon input to the Arctic Ocean

Journal information: Geology

Provided by Cardiff University
Citation: Why does our planet experience an ice age every 100,000 years? (2016, October 26) retrieved 22 September 2019 from https://phys.org/news/2016-10-planet-ice-age-years.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
140 shares

Feedback to editors

User comments

Oct 26, 2016
Why does our planet experience an ice age every 100,000 years?


Because the Climate Changes©

Oct 26, 2016
New research published today in the journal Geology has suggested the oceans may be responsible for this change, specifically in the way that they suck carbon dioxide (CO2) out of the atmosphere.


Man they must be reading my posts on phys.org, I have been saying this for years now.

So that begs the question, what caused the big change in frequency from 40K years to 100K.

One guess is that the plate tectonics opened up a new avenue for oceans to circulate, causing the cycle to alter.

Oct 26, 2016
LOL.
Climate change is NATURAL. It's the oceans stupid.

In addition to these natural cycles, manmade carbon emissions are also having an effect by warming the climate.

But, you got to love how they must feed the hunger of the AGW Cult's ignorant Chicken Littles. Has manmade CO2 altered these natural cycles?
NO. Then we have no influence.

Oct 26, 2016
LOL.
Climate change is NATURAL. It's the oceans stupid.

Interesting that they were able to establish a cyclicity to it. I wonder if the change was sudden or gradual...

Oct 26, 2016
I wonder if the change was sudden or gradual

Well given the study done saying the AMOC could change within a 1000 years, and we have temperature records to back up those findings, I'd say it's pretty sudden from a geological viewpoint.

Oct 26, 2016
I wonder if the change was sudden or gradual

Well given the study done saying the AMOC could change within a 1000 years, and we have temperature records to back up those findings, I'd say it's pretty sudden from a geological viewpoint.


Since your records go back a measly 150 years at best, I would say you have nothing from a geological viewpoint.

Oct 26, 2016
The Panama Hypothesis posits that there was no permanent Northern hemispheric ice cap until about 3.5 mya after the isthmus formed. This stopped eater exchange between the Pacific and Atlantic oceans, the Gulf Stream carried moist air concentrating more precipitation over Siberia which decreased the salinity of the Arctic ocean causing it to freeze. Others also attribute the Western U.S. mountain formation. The 40 k and 100 k cycles correspond to the Milankovitch orbital cycles. The ocean CO2 dynamic might be dependent on the orbital cycles and geological changes due to plate tectonics.

Oct 26, 2016
I wonder if the change was sudden or gradual

Well given the study done saying the AMOC could change within a 1000 years, and we have temperature records to back up those findings, I'd say it's pretty sudden from a geological viewpoint.

Reference? I mean how fast could the AMOC generate or degrade an Ice age?
Since your records go back a measly 150 years at best, I would say you have nothing from a geological viewpoint.

Sorry Sam, but there have been plenty of geologic samplings that allow for derivation of temperature variations over a LO-O-o-ong, long time...
See - https://en.wikipe...e_record , for example.
(And before you slam Wiki - the authors are professional engineers and scientists who volunteer their spare time to keep it updated. The may not have their names listed, but they are vetted pretty well.)

Oct 27, 2016
I wonder if the change was sudden or gradual

Well given the study done saying the AMOC could change within a 1000 years, and we have temperature records to back up those findings, I'd say it's pretty sudden from a geological viewpoint.

what I Meant was -
did it happen a million years ago over a single cycle or did it take 4 or 5 to build up to it...

Oct 27, 2016
The problem with the theory is that were it true you should find higher concentrations of CO2 in ice core samples that are consistent with the 100 000 year problem.

Oct 27, 2016
This theory fails to explain two key elements of ice ages — When CO2 reaches minimum concentrations, the world warms. And when CO2 reaches maximum concentrations, the world cools.

So what mechanism modulates the 100 ky cycle? Ok - ice naturally grows in our present climate, until something stops and reverses it. That process involves CO2 getting so low that all upland plants die, causing vast CO2 deserts in China. (Yes, CO2 deserts, not aridity deserts.) Dust from these new deserts was lifted up and deposited on the ice sheets, lowering their albedo and allowing them to absorb more insolation, which precipitates rapid melting. The evidence for these dust eras is in the ice core record. CO2 concentrations take no part in this warming process, apart from getting so low that nearly all upland plant-life is asphyxiated. Thus the CO2 theory is not supported by the ice age cycle. See paper: 'Modulation of Ice Ages by Dust Albedo'.

Oct 27, 2016
This comment has been removed by a moderator.

Oct 27, 2016
After Reading this article and everyone's comments, I feel like no one has any Complete ideas as to why the ice ages occur. Why would CO2 concentrations get low? and if them being low during an ice age causes the planet to get colder, what makes it warm up? It sounds like Snowball Earth theory, yet they are saying it cycles, yet no explanation of the Cycle itself.

Oct 27, 2016
WG, the link is below:
http://phys.org/n...ate.html
"The series of abrupt climate changes studied here occurred between 60,000 and 25,000 years ago, ending as the last ice age peaked. Each followed a general pattern in the Northern Hemisphere: The cooling happening over hundreds to 1,000 years, then the frigid temperatures persisted for a few hundred years in what is known as a stadial, McManus said. Once warming started, it happened very rapidly, with a rise of 3 to 6 degrees Celsius in average sea surface temperature and larger changes over Greenland within a span of decades."

SamB, see above...

Oct 27, 2016
This comment has been removed by a moderator.

Oct 27, 2016
did it happen a million years ago over a single cycle or did it take 4 or 5 to build up to it...

Ahh I gotcha. That's hard to say, but looking at the temp history I'd say it took a few cycles to establish the new regime:
http://www.giss.n...fig1.gif

Oct 27, 2016
However there was a point, about a million years ago, called the 'Mid-Pleistocene Transition', in which the ice age intervals changed from every 40,000 years to every 100,000 years
In the plane of the galaxy the Sun is located in the spiral Orion arm between the two nearest major spiral arms (the Sagitarius and Perseus arms). We pass through the Galactic midplane about every 35 million years. In addition, we pass through a major spiral arm about every 100 million years, taking about 10 million years to go through. During the transit, there would be a higher rate of 'nearby' supernova and possibly other so called 'environmental stresses' which could alter http://adsabs.har...8113312.

While not outside the realm of possibility, that's a bit of a fractal connection stretch, isn't it Zeph...?

Oct 27, 2016
This theory fails to explain two key elements of ice ages — When CO2 reaches minimum concentrations, the world warms. And when CO2 reaches maximum concentrations, the world cools.

Want a "farmers" explanation?
The warmer it gets, the more water in the atmosphere (Clouds). The more clouds, the more reflective the atmosphere. The more reflective the atmosphere, the cooler it gets. And so it trickles on down...
Oh, and the CO2? Gets scrubbed out by all the rain...
I also have a story bout how a warmer planet releases a huge amount of methane. It's called "Don't light that ma-!"
You can guess how it ends...:-)


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more