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

More Warmist rubbish -- confusing cause and effect again. Of course there was more CO2 dissolved in the oceans during cooler periods.  That is what cooler water does.  It dissolves more CO2.  Your Coca Cola would not fizz otherwise. So they really have no causal explanation at all for the matter they discuss

I add the journal abstract following the popular summary below.  The opening comments of the abstract indicate that the period of cyclicity was cooler  as a whole.  I quote: "The ~100 k.y. cyclicity of the late Pleistocene ice ages started during the mid-Pleistocene transition (MPT), as ice sheets became larger and persisted for longer"

Only a carefully dated tabulation of temperature and CO2 levels showing which changes came first could establish the theory they offer. They offer nothing of that sort.  They report on CO2 proxies only

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 carbon dioxide (CO2) out of the atmosphere.

By studying the chemical make-up of tiny fossils on the ocean floor, 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 atmosphere when deep ocean 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 ocean,” 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.


Breathing more deeply: Deep ocean carbon storage during the mid-Pleistocene climate transition

Lear, Caroline et al.


The ~100 k.y. cyclicity of the late Pleistocene ice ages started during the mid-Pleistocene transition (MPT), as ice sheets became larger and persisted for longer. The climate system feedbacks responsible for introducing this nonlinear ice sheet response to orbital variations in insolation remain uncertain. Here we present benthic foraminiferal stable isotope (d18O, d13C) and trace metal records (Cd/Ca, B/Ca, U/Ca) from Deep Sea Drilling Project Site 607 in the North Atlantic. During the onset of the MPT, glacial-interglacial changes in d13C values are associated with changes in nutrient content and carbonate saturation state, consistent with a change in water mass at our site from a nutrient-poor northern source during inter- glacial intervals to a nutrient-rich, corrosive southern source during glacial intervals. The respired carbon content of glacial Atlantic deep water increased across the MPT. Increased dominance of corrosive bottom waters during glacial intervals would have raised mean ocean alkalinity and lowered atmospheric pCO2. The amplitude of glacial-interglacial changes in d13C increased across the MPT, but this was not mirrored by changes in nutrient content. We interpret this in terms of air-sea CO2 exchange effects, which changed the d13C signature of dissolved inorganic carbon in the deep water mass source regions. Increased sea ice cover or ocean strati cation during glacial times may have reduced CO2 outgassing in the Southern Ocean, providing an additional mechanism for reducing glacial atmospheric pCO2. Conversely, following the establishment of the ~100 k.y. glacial cycles, d13C of interglacial northern-sourced waters increased, perhaps re ecting reduced invasion of CO2 into the North Atlantic following the MPT.


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