Fresh understanding of ice age frequency – Otago study

Posted: December 7, 2022 by oldbrew in climate, Cycles, Ice ages, Natural Variation, paleo, research

Ross Ice Shelf, Antarctica

By saying, of Antarctica’s ice sheets, “this research shows they actually advanced and retreated much more often – every 41,000 years – until at least 400,000 years ago”, the research adds a new twist to the longstanding 100,000 year problem of ice ages. It puts obliquity firmly back in the frame.
– – –
A chance find of an unstudied Antarctic sediment core has led University of Otago researchers to flip our understanding of how often ice ages occurred in Antarctica, says Eurekalert.

Lead author Dr Christian Ohneiser, of the Department of Geology, says it turns out they were much more frequent than previously assumed.

“Until this research, it was common knowledge that over the last million years global ice volume, which includes Antarctica’s ice sheets, expanded and retreated every 100,000 years.

“However, this research shows they actually advanced and retreated much more often – every 41,000 years – until at least 400,000 years ago,” he says.

The study, published in Nature Geosciences, came about after Dr Ohneiser sampled a sediment core from the Ross Sea for a different project which was designed to reconstruct the retreat of the Ross Ice Shelf after the last ice age.

“The 6.2 metre core was recovered in 2003 and placed in an archive in the US, but was not studied further. I sampled it because I was expecting the core to have a record spanning the last 10,000 or so years.

“I conducted a paleomagnetic analysis on the core, which reconstructs changes in the earth’s magnetic field, and found a magnetic reversal showing it was much older and had a record spanning more than 1 million years.”

Sedimentary and magnetic mineral indicators enabled Dr Ohneiser to reconstruct how big the Ross Ice Shelf, and the West Antarctic Ice Sheet which feeds the shelf, were.

“Ice bergs, which come from the ice shelf, have sediment and rocks attached to their underside. When icebergs break off they float out to sea and drop the rocks and sediment as it melts, these rocks and sediments can also come directly from the ice shelf if the ice was over the core site.

“By figuring out how much of this debris is in the core through time we can build a picture of the changes in the size of the ice sheet,” he says.

Previous understanding of ice age frequencies was based on assumptions and incomplete data sets, but knowledge of them is important as the world faces climate change.

Full press release here.
– – –
Study: West Antarctic ice volume variability paced by obliquity until 400,000 years ago
Quote: ‘Our study reconciles the historical mismatch between the inferred glacial cycles and the insolation record.’

  1. Phil Salmon says:

    It’s always been obliquity, the apparent 100,000 period is a modulation of obliquity (and precession) although the resemblance to eccentricity is not coincidental.

    Nice to have this confirmed by a super-valuable new pristine 1.1 million year marine sediment core (of ice-rafted debris). Yay 😀

  2. Chaswarnertoo says:

    Proper science.

  3. oldbrew says:

    In our orbital resonance model, the 123 kyr period is 3 obliquities (the period where 0.3 long eccentricity and 1.3 short eccentricity cycles have a difference of 1, i.e. a frequency of 10 at the 3:13 ratio). See the blue triangle in Figure 1 here…

  4. brianrlcatt says:

    Why is this being promoted. It is very well Known.

    “Previous understanding of ice age frequencies was based on assumptions and incomplete data sets, but knowledge of them is important as the world faces climate change.” This appears to be meaningless twaddle.

    We are looking at 1/ 2 deg solar cycle climate change with a 1Ka period, not the much longer period ice age cycles, which will tend to make it colder, as indeed they have for the last 3,000 years of the current neo glacial that began at the end of the Holocene Optimum, consistent with at least the last 4 interglacial cycles.

    It’s undergrad teaching as far as describing the ice ages and also demonstrating the extraction of the 3 Milankovitch frequencies that are well seen within their convolved effect of the ice age cycle temperature time series. The earlier 41Ka cycles dominance is also well known from the observed records. And as a component of the 100Ka cycle. It is also wrong because the natural cycle is being reported as 100Ka, which it is not. While the 100Ka cycle currently dominates, the actual resultant cycle length of the convolved effects of all three varies considerably, according to their relative phase hence interference product of the three main orbital forcing cycles. To see this working use this High school toy created by the University of Madison. As this guy should have done. Ice sheets come and go all the time, to the tune of all three orbital forcing periods.

    What interested me about this was the 100Ka eccentricity maximum has net zero insolation effect yet is is more energetic overall than the short sharp effect of the 41Ka obliquity cycle that first dominated this ice age series of glaciations, so it seems insolation is not the major cause of the less intense but longer lasting 100Ka eccentricity cycle.

    I suggest the orbital forcing is gravitational and causes a significant increase in submarine volcanism to 3-4 times the average over the 20Ka or so of the interglacial event, more times the minimum that is the steady state glacial phase. The effect of gravitational orbital forcing peaks is to create maximums in the solid tides in the visco elastic Earth, and hence the known maximums in volcanic activity as it twerks to the three different beats.

    The solid tidal effect is also well known, the land and sea floor surface is in constant 3D motion from daily lunar to 100Ka solar orbital cycles.. There are many more and more productive submarine volcanoes than there are sub aerial, whose heat directly warms the oceans that store the heat for much longer, rather than being quickly lost to space as with sub-aerial volcanoes. The total output of submarine volcanoes must be at least 20 times the output of sub aerial volcanoes, simply by known productivity and pro rata numbers using ocean vs. land area. Hence the steady warming of the oceans as their levels rise throughout the interglacial warmings, and continued to rise throughout the Younger Dryas event of our Holocene warming, while land surface temperatures temporarily returned to glacial for nearly 2,000 years if the usual 7Ka interglacial warming period, while the oceans still continued to thaw the land ice with warm enough rain to create a steady net thaw, so the oceans continued to rise and get the warming cycle back on track that we now experience as the relatively cool interglacial Holocene, because the peak was lost. Also note that the planetary cooling response hits turbo power as the tropics oceans reach around 28 deg, to halt both 41Ka and 100Ka interglacial warming events at a tropically saturated 28 degrees, the tropics then must extend this effect as far towards the poles as it takes to maintain the equilibrium SST, hence Hippos in Honiton at 50 deg N and S during the Eemian, when all three Milankovitch cycles were in phase and the polar temperatures were 4 degrees warmer than this interglacial. Stability required tropical heat loss rates at 50 deg from the Equator. Who knew? Geologist did, ages ago, remember this graph?

  5. […] Fresh understanding of ice age frequency – Otago study — Tallbloke’s Talkshop […]

  6. Ned Nikolov, Ph.D. says:

    I’m not sure when this confusion will end, but the paleo-climate record combined with our modern understanding of orbital variations (i.e. obliquity, eccentricity and precession as modeled by Laskar et al. 2004 and 2011) clearly shows that there is no consistent relationship between orbital dynamics and the occurrence and progression of Ice Ages over the past 800 Ky. See this blog post:

    Ned Nikolov: Dispelling the Milankovitch Myth

    Also, modern NASA observations of planets and moons in the Solar System representing a range of obliquities do not provide evidence that obliquity has a measurable impact on the long-term global surface temperature of planetary bodies. If obliquity did affect the global temperature, then our pressure-temperature relationship across 6 planetary bodies would not have been possible, since it does not consider obliquity:

    It’s time to abandon the 80-year old myth that Ice Ages were driven by Milankovitch cycles! There were NOT!

  7. They wrote:
    “However, this research shows they actually advanced and retreated much more often – every 41,000 years – until at least 400,000 years ago,”

    I knew that a decade ago, that is not new information. we have had 4 major ice ages with ice core records that go back 400 thousand years and before that were 41 thousand year cycles.

  8. Ned Nikolov, Ph.D. says:

    This video presented at the 101st AMS Meeting in Jan of 2021 provides a new explanation for the Ice Ages. We found that changes of total atmospheric mass and surface pressure must be the real driver of Ice Ages, because such changes accurately reproduce the Polar Amplifications observed in the geological record during glacial cycles:

    The surface temperature of any planet and moon is determined by diabatic heating through the Sun and an adiabatic enhancement of the solar energy via atmospheric pressure. The evidence clearly shows that orbitally induced changes in the Top-Of-the-Atmosphere (TOA) Total Solar Irradiance (TSI) are too small to significantly affect Earth’s global temperature during the past 800 Ky. And yes, changes of obliquity cannot explain global temperature variations between glacial and interglacial states either! So, the only option left is a variation of the adiabatic forcing, i.e. total air pressure. This correctly describes the observed changes in the Equator-to-Pole temperature gradient during the Ice Ages… Watch the above video for details.

  9. oldbrew says:

    The study abstract says:

    Here we present sedimentological and palaeomagnetic records from a 6.21-metre-long sediment core spanning the last 1.1 million years that track the proximity of the ice margin in the Ross Embayment. The advance and retreat of the Ross Ice Shelf—and by extension the West Antarctic Ice Sheet—are found to have been primarily paced by 41,000-year-long obliquity cycles until at least 400,000 years ago.

    The full study isn’t open access.
    – – –
    This graph is on the Wikipedia ‘100,000 year problem’ page.

    It says ‘The source of the data shown in the graph is unknown’, but the graph itself is from NASA/GISS and has something to do with Gavin Schmidt.

    As an initial observation, the gap between ‘modern climate’ and ‘last warm period’ looks to be around 3 obliquities (~123-125 kyr). On the other hand we don’t know exactly what data was used, only that it’s an average of the readings.

  10. oldbrew says:

    A recent study ‘investigated a sediment core from the eastern Mediterranean documenting temperatures from the last interglacial period (from around 129,000 to 116,000 years ago). The study by Obreht and colleagues thus centered on the last time that temperatures were warmer than they are today.’

    That would centre on about 3 obliquities or ~124,000 years.

    DECEMBER 7, 2022
    Climate archives under the magnifying glass
    by MARUM – Center for Marine Environmental Sciences, University of Bremen

    NB the article starts with a new study in Venezuela re. the Holocene of 11,700 years ago. The Mediterranean one mentioned later was published in September.

  11. Ned Nikolov, Ph.D. says:


    Trying to describe the periodicity of Ice Ages as a multiplier of the obliquity cycle is physically meaningless…

  12. oldbrew says:

    This article starts off quite well but sinks into greenhouse gas waffle towards the end.

    Ice ages have been linked to the Earth’s wobbly orbit – but when is the next one?
    By: Mark Maslin
    Professor of Palaeoclimatology, UCL
    Published: December 9, 2016

    Over the last two and a half million years the Earth has undergone more than 50 major ice ages, each having a profound effect on our planet’s climate. But what causes them and how do we predict when the next big ice age will hit?
    . . .
    Beyond wobbles
    However, the scientists realised that there were limitations and challenges of their research – many of which remain today. In particular, they recognised that variations in the Earth’s orbit did not cause the ice age cycles per se – they rather paced them. A certain orbit of the Earth can be associated with many different climates. The one we have today is in fact similar to the one we had during the most intense part of the last ice age.
    – – –
    Another paper says:
    We combine an Italian speleothem record anchored by a uranium-lead chronology with North Atlantic ocean data to show that the first two deglaciations of the so-called 100,000-year world are separated by two obliquity cycles, with each termination starting at the same high phase of obliquity, but at opposing phases of precession. An assessment of 11 radiometrically dated terminations spanning the past million years suggests that obliquity exerted a persistent influence on not only their initiation but also their duration.

    Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition (2020)

    Obviously I can’t say if their conclusions are right, but there seems to be lot of research along these lines.

  13. Ned Nikolov, Ph.D. says:


    Yes, there are occasional correlations between obliquity and Ice Ages, but in order for this to be a causative mechanism, the relationship between obliquity and Ice-Age termination and/or durations must be strong and occurring every time. However, observations fail to show this. So, they use the vague term “pace” instead of “cause” to describe the “effect” of obliquity on Ice Ages. This is not very helpful in finding the actual driver… 🙂

  14. oldbrew says:

    OK, thanks Ned. Interesting new paper…

    Published: 03 October 2022
    Complex spatio-temporal structure of the Holocene Thermal Maximum

    Here, we analyze a global database of Holocene paleotemperature records to investigate the spatiotemporal structure of the HTM. Continental proxy records at mid and high latitudes of the Northern Hemisphere portray a “classic” HTM (8–4 ka). In contrast, marine proxy records from the same latitudes reveal an earlier HTM (11–7ka), while a clear temperature anomaly is missing in the tropics. The results indicate a heterogeneous response to climate forcing and highlight the lack of globally synchronous HTM.

    …[later in the paper]…
    The latitudinal pattern in the timing of marine HTM is most likely steered by orbital forcing, because it is the largest contributor to radiative forcing, especially during the early Holocene (Figs. 3, 8–10). article on it:
    The last 12,000 years show a more complex climate history than previously thought
    OCTOBER 4, 2022

    According to the lead author Olivier Cartapanis, “the results challenge the paradigm of a Holocene Thermal Maximum occurring at the same time worldwide.” And, while the warmest temperature was reached between 4,000 and 8,000 years ago in western Europe and northern America, the surface ocean temperature cooled since about 10,000 years ago at mid-high latitudes and remained stable in the tropics. The regional variability in the timing of maximum temperature suggests that high latitude insolation and ice extent played major roles in driving climate changes throughout the Holocene.
    – – –
    ‘ice extent played major role in driving climate changes’ — sounds like the cart going before the horse again 🙄

  15. oldmanK says:

    This thread starts with the words “Fresh understanding”, when in fact the references to obliquity are based on the work of J N Stockwell from 1872. They only refer to the Secular changes. (added: and limited to)

    There have been others that questioned the matter, namely R R Newton being an important one.
    particularly chapter 6 >> “6. Non-Gravitational Changes in the Obliquity”

    The background story is here, and it is interesting how it developed into a sort of dogma.

    Obliquity, and associated with it Precession (they act together) are inherent dynamics of the earth and effected by other planetary influences in particular circumstances as in planet conjunctions. ( stand to be corrected here, but if I got the impression correct from Stockwell’s work/book, there was no consideration of the effect of conjunctions. I think Kepler had other ideas).

  16. Ned Nikolov, Ph.D. says:


    Thank you for the reference to this new paper on the Holocene Thermal Maximum (HTM):

    The results presented by the authors are puzzling, because they suggest a vastly different timing of HTM over land compared to oceans. The peaks of HTM over land and oceans are separated by about 3,500 years, which make no physical sense. If the global SST peaked at about 9.5 Ky ago due to whatever forcing, how come this early ocean warming did not affect the temperatures of continents, if the oceans cover 70% of the Earth’s surface?

    The authors provide no explanation for the reported odd temporal separation of HTM between land and ocean. One possible explanation, which the authors dismiss, might be seasonally biased marine temperature proxies… At any rate, this study seams to downplay the significance of HTM by stating that HTM was NOT globally synchronous. Let’s not forget that a globally synchronous HTM does not fit well with the concept of a CO2-forced deglaciation, because the CO2 forcing is estimated to have continuously been increasing for the past 10 Ky as shown in their Fig. 8:

  17. oldbrew says:

    Even if there was a hemispheric split in HTM it’s hard to imagine how a 3000+ year difference could make sense.

  18. Ned Nikolov, Ph.D. says:

    They are not claiming a hemispheric difference in the timing of HTM, but a 3,500-year lag in the HTM occurrence over land compared to oceans, which is even stranger!

    It could be that the authors had a hidden agenda to eliminate the HTM as a global phenomenon, since it interferes with the concept that a CO2 forcing was responsible for ending the last Ice Age.

  19. oldbrew says:

    From the HTM study:
    ‘This discrepancy between proxy data and model simulations, commonly referred to as “The Holocene Temperature Conundrum”, casts doubt on the conceptual framework underlying temperature proxy interpretation and on climate model skill.’
    – – –
    Casting doubt on climate model skill? Oh dear 😉

  20. oldbrew says:

    DECEMBER 13, 2022
    Changes in Earth’s orbit may have triggered ancient warming event
    by Matthew Carroll, Pennsylvania State University

    They found the shape of Earth’s orbit (eccentricity), and the wobble in its rotation (precession), favored hotter conditions at the onset of the PETM and that these orbital configurations together may have played a role in triggering the event.

    “An orbital trigger may have led to the carbon release that caused several degrees of global warming during the PETM as opposed to what’s a more popular interpretation at the moment that massive volcanism released the carbon and triggered the event,” said Kump, the John Leone Dean in the College of Earth and Mineral Sciences.

    The findings, published in the journal Nature Communications, also indicated the onset of the PETM lasted about 6,000 years. Previous estimates have ranged from several years to tens of thousands of years. The timing is important to understand the rate at which carbon was released into the atmosphere, the scientists said.
    – – –
    They seem to be back on the ‘CO2 rise preceded warming’ theory, contradicted by ice cores.

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