Research sheds new light on what drove last, long-term global climate shift

December 19, 2018, University of Exeter
Credit: CC0 Public Domain

The quest to discover what drove the last, long-term global climate shift on Earth, which took place around a million years ago, has taken a new, revealing twist.

A team of researchers led by Dr. Sev Kender from the University of Exeter, have found a fascinating new insight into the causes of the Mid-Pleistocene Transition (MPT) - the phenomenon whereby the planet experienced longer, intensified cycles of extreme cold conditions.

While the causes of the MPT are not fully known, one of the most prominent theories suggests it may have been driven by reductions in glacial CO2 emissions.

Now, Dr. Kender and his team have discovered that the closure of the Bering Strait during this period due to glaciation could have led the North Pacific to become stratified—or divided into distinct layers—causing CO2 to be removed from the atmosphere. This would, they suggest, have caused global cooling.

The team believe the latest discovery could provide a pivotal new understanding of how the MPT occurred, but also give a fresh insight into the driving factors behind global climate changes.

The research is published in Nature Communications on December 19th 2018.

Dr. Kender, a co-author on the study from the Camborne School of Mines, based at the University of Exeter's Penryn Campus in Cornwall said: "The subarctic North Pacific is composed of some of the oldest water on Earth, which has been separated from the atmosphere for such a long time that a high concentration of dissolved CO2 has built up at depth. When this water upwells to the surface, some of the CO2 is released. This is thought to be an important process in geological time, causing some of the that followed past glaciations.

"We took deep sediment cores from the bottom of the Bering Sea that gave us an archive of the history of the region. By studying the chemistry of sediment and fossil shells from marine protists called foraminifera, we reconstructed plankton productivity, and surface and bottom water masses. We were also able to better date the sediments so that we could compare changes in the Bering Sea to other global changes at that time.

"We discovered that the Bering Sea region became more stratified during the MPT with an expanded intermediate-depth watermass, such that one of the important contributors to global warming—the upwelling of the subarctic North Pacific—was effectively curtailed."

The Earth's climate has always been subjected to significant changes, and over the past 600,000 years and more it has commonly oscillated between warm periods, similar today, and colder, 'glacial' periods when large swathes of continents are blanketed under several kilometres of ice.

These regular, natural changes in the Earth's climate are governed by changes in how the Earth orbits around the sun, and variations in the tilt of its axis caused by gravitational interactions with other planets.

These changes, known as orbital cycles, can affect how solar energy is dispersed across the planet. Some orbital cycles can, therefore, lead to colder summers in the Northern Hemisphere which can trigger the start of glaciations, while later cycles can bring warmer summers, causing the ice to melt.,

These cycles can be influenced by a host of factors that can amplify their effect. One of which is CO2 levels in the atmosphere.

As the MPT occurred during a period when there were no apparent changes in the nature of the orbit cycles, scientists have long been attempting to discover what drove the changes to take place.

For this research, Dr. Kender and his team drilled for deep-sea sediment in the Bering Sea, in conjunction with the International Ocean Discovery Program, and measured the chemistry of the fossil shells and sediments.

The team were able to create a detailed reconstruction of oceanic water masses through time—and found that the closure of the Baring Strait caused the subarctic North Pacific became stratified during this period of glaciation.

This stratification, that argue, would have removed CO2 from the atmosphere and caused global cooling.

Dr. Kender added: "Today much of the cold water produced by sea ice action flows northward into the Arctic Ocean through the Bering Strait. As glaciers grew and sea levels fell around 1 million years ago, the Bering Strait would have closed, retaining colder water within the Bering Sea. This expanded watermass appears to have stifled the upwelling of deep CO2-rich water and allowed the ocean to sequester more CO2 out of the atmosphere. The associated cooling effect would have changed the sensitivity of Earth to orbital cycles, causing colder and longer glaciations that characterise climate ever since.

"Our findings highlight the importance of understanding present and future changes to the high latitude oceans, as these regions are so important for long term sequestration or release of atmospheric CO2."

Explore further: Formation of coastal sea ice in North Pacific drives ocean circulation and climate

More information: Sev Kender et al, Closure of the Bering Strait caused Mid-Pleistocene Transition cooling, Nature Communications (2018). DOI: 10.1038/s41467-018-07828-0

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17 comments

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Anonym
1 / 5 (7) Dec 19, 2018
But of course they have no way of knowing there was no orbital anomaly during the period. You have to consider the source of these "climate change" studies, and those from the U of Exeter have a strong anthropogenic bias. "Seek and ye shall find" is their guiding principle. These are the same folks who were predicting an ice-free pole by 2020, polar bear extinction, and the disappearance of snow from the UK's winter landscape. LOL.
aksdad
1 / 5 (5) Dec 19, 2018
...the closure of the Bering Strait during this period due to glaciation could have led the North Pacific to become stratified—or divided into distinct layers—causing CO2 to be removed from the atmosphere

The crucial phrase here is "could have". Or it couldn't have.

We are so stuck on the CO2-generated-warming hypothesis that it doesn't occur that atmospheric CO2 may be an effect of warming, not a cause. By far the largest source of CO2 production is microbial and plant respiration and decomposition.

It is just as plausible that some event caused cooling (changes in ocean circulation, orbital changes, large meteor impact, large-scale volcanism on the surface or in the deep ocean, etc.), and since cooling reduces plant and microbial biomass, CO2 also is reduced. Correlation is not causation, folks. Try a little more creative thinking.
Bongstar420
1 / 5 (6) Dec 19, 2018
It was geographical stuff effecting ocean currents combined with all the usual forcers except CO2. CO2 is not a primary driver though this doesn't give the oil billionaires and all you consumers a get out of jail free card. You are still guilty of holding us back with primitive technology. Opposing oil because the environment is a chimps errand.

CO2 reduces over long time scales due to geochemical effects. Volcanism creates cycles of input and output CO2 on massive diffuse scales which are hardly measurable due to the low intensity, wide distribution.
Da Schneib
4.2 / 5 (5) Dec 19, 2018
But of course they have no way of knowing there was no orbital anomaly during the period.
Sure they do. We'd be able to see the results today in ephemerides. Maybe you should google ephemerides up. We make them every year.
Da Schneib
4.2 / 5 (5) Dec 19, 2018
Here's one the taxpayers pay for, so it's free: https://ssd.jpl.n...emerides
Bert_Halls
4.4 / 5 (7) Dec 19, 2018
Anonym, Aksdad, and Bongstar420 are shills. They need to be banned from speaking.

No, not banned from this website. I'm thinking surgical intervention to remove their vocal cords. And fingers, for good measure.
antigoracle
1 / 5 (6) Dec 19, 2018
As glaciers grew and sea levels fell around 1 million years ago, the Bering Strait would have closed

More astonishing bullshit from the AGW Cult and their PATHOLOGICAL "SCIENCE", just to feed their ignorant, hungry Chicken Littles.
So, what initially caused the cooling that resulted in growing glaciers and the Bering Strait closing?
Da Schneib
4 / 5 (4) Dec 20, 2018
Ahh, the perils of not actually reading the article and doing some research.
V4Vendicar
5 / 5 (5) Dec 20, 2018
But of course they have no way of knowing there was no orbital anomaly during the period.


You mean like the one that happened when planet meta-luna flew past the earth 3 million years ago?

You are, of course, a low grade moron who wears a tin foil cap.

V4Vendicar
5 / 5 (6) Dec 20, 2018
"More astonishing bullshit from the AGW Cult and their PATHOLOGICAL "SCIENCE"" - Antigorical

More futile ignorance from the uneducated online idiot that calls itself Antigorical.
V4Vendicar
5 / 5 (5) Dec 20, 2018
"CO2 may be an effect of warming, not a cause" - aksdad

Ya, the world may be heating because of them alien moon beams that don't make it past your tinfoil hat.

"It is just as plausible that some event caused cooling" - aksdad

To a tinfoil hatter like you everything is just as plausible because you are scientifically illiterate.
Da Schneib
3.7 / 5 (3) Dec 20, 2018
While doing my research I found that while the Milankovic orbital cycles have determined the glacial/interglacial cycle over the last million years or so, this was not so true before that back to the beginning of the Pleistocene (another million years). And nobody knows why. The geophysicists are still arguing about it.
Whydening Gyre
5 / 5 (3) Dec 20, 2018
But of course they have no way of knowing there was no orbital anomaly during the period. You have to consider the source of these "climate change" studies, and those from the U of Exeter have a strong anthropogenic bias. "Seek and ye shall find" is their guiding principle. These are the same folks who were predicting an ice-free pole by 2020, polar bear extinction, and the disappearance of snow from the UK's winter landscape. LOL.

Still have a year to go....
SteveS
3 / 5 (1) Dec 20, 2018
"Seek and ye shall find" is their guiding principle.


No it's not, it's Lucem sequimur - We Follow The Light.
antigoracle
1 / 5 (3) Dec 20, 2018
Ahh, the perils of not actually reading the article and doing some research.

Da Snob, the "meat" loving, knob gobbling, jackass brays again.
Ahh, the perils of having the shite between his ears being rattled as his boyfriend tries to "research" that "sweet spot" in his rectum.
Was he born this stupid, or has he been practicing.
V4Vendicar
5 / 5 (2) Dec 21, 2018
antigoracle hasn't been the same since he tweeted about seeing those martian sand dunes having sex.

He isn't all right in the head.
V4Vendicar
5 / 5 (3) Dec 21, 2018
"his was not so true before that back to the beginning of the Pleistocene "

CO2 levels fell so the planet cooled allowing the orbital cycles to play a more significant roll in guiding temperatures.

Even today the global temperature does not precisely match solar insolation. The system has various natural periods and latentcies that delay the trigger to a glacial or interglacial. Those triggers become less potent as CO2 levels and hence global temperatures rise.

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