How ancient dust from the sea floor helps to explain climate history

A research team led by geoscientists of the University of Oldenburg, Germany, analyzed sediment cores from the South Pacific

UNIVERSITY OF OLDENBURG

Research News

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IMAGE: 18 SEDIMENT CORES FROM THE SEABED WERE BROUGHT ON BOARD THE RESEARCH VESSEL “POLARSTERN ” BY MEANS OF PLUNGERS AND GRAVITY SOUNDERS. view more CREDIT: KATHARINA PAHNKE / UNIVERSITY OF OLDENBURG

During the last Ice Age about 20,000 years ago, iron-containing dust acted as a fertilizer for marine phytoplankton in the South Pacific, promoting CO2 sequestration and thus the glacial cooling of the Earth. But where did the dust come from? Researchers led by Dr. Torben Struve, geoscientist at the University of Oldenburg, Germany, have investigated this open question of climate history, which is also relevant with respect to current climate change.

Using sediment cores from the sea floor, they found that a large part of the dust deposited in the southern South Pacific at that time had travelled an extremely long way. Up to 80 percent of the dust came from what is now north-west Argentina, from where it was transported almost completely around the globe by the prevailing westerly winds. After a voyage of up to 20,000 kilometres, it contributed significantly to the increased input of iron into the glacial South Pacific. The dust input from Australia, which dominates in the South Pacific today, played only a minor role. The research team has published these new insights into the mechanisms of natural iron input into the Southern Ocean in the journal Nature Communications.

“We have analysed the chemical fingerprint of the dust and compared it with geological data from several continents. This was laborious work, like a jigsaw puzzle,” says Struve, a post-doctoral scientist in the research group “Marine Isotope Geochemistry” at the University’s Institute for Chemistry and Biology of the Marine Environment (ICBM). The team included researchers from his group as well as colleagues from the Alfred Wegener Institute – Helmholtz Centre for Polar and Marine Research, Bremerhaven (Germany), and from Columbia University, New York (USA).

The researchers sampled 18 sediment cores from the South Pacific between Antarctica, New Zealand and Chile, a study area which is roughly the size of Russia. Subsequently, they investigated the chemical composition of the dust contained in the samples. “This dust ultimately stems from rock, which has characteristic properties depending on its place of origin and geologic history so that each source has its own signature,” Struve explains.

The researchers focused on trace metals, in particular rare earth elements and specific isotopes, that is variants of different weight, of the elements neodymium, lead and strontium. This signature is preserved over millions of years and thus provides reliable information about the origin of rock particles even after 20,000 years.

At that time, the last Ice Age was at its peak. According to the results, westerly winds blew dust particles from the eastern side of the central Andes in South America across the Atlantic and the Indian Ocean. As such, the iron-bearing dust was transported once around the globe before being deposited in the middle latitudes of the South Pacific. Since algae in these waters usually lack iron as a crucial nutrient for growth, iron-containing dust acts as a natural fertiliser until today.

Like all plants, phytoplankton – microscopic algae – absorbs carbon by means of photosynthesis and thus reduces the proportion of carbon dioxide (CO2) in the atmosphere. According to Struve, the greatly increased input of iron-bearing mineral dust into this marine region, primarily from South America, could help to explain “how the Earth could have become so cold at all at that time”.

It was already known that the iron input during the last ice age was much higher than during the present warm period. “But we were surprised to find that the sources and transport routes of the dust were completely different from today and also different from what we would have expected.”

The research team concludes that the unusually high dust emissions from South America must have made a significant contribution to the reduction of CO2 in the atmosphere of the Ice Age. The input of iron-bearing mineral dust reduced the CO2 level of the atmosphere by up to 40 ppm (“parts per million”). This corresponds to almost half of the natural CO2 variation in the atmosphere over the last 400,000 years amounting to 100 ppm. To put this into perspective, since the beginning of industrialisation, anthropogenic emissions have increased the CO2 level from around 280 to around 415 ppm.

Today, no dust from South America can be detected in the study area. “Global warming has changed the winds and environmental conditions in the source regions,” Struve says, who continues to study the sediment cores. Together with his colleagues, he wants to find out how the composition of the dust has changed since the peak of the ice age and how this may have contributed to climate change.

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From EurekAlert!

49 thoughts on “How ancient dust from the sea floor helps to explain climate history

    • In fact, in this case they might have a point. At the end of the last glacial period, CO2 levels dropped blow 200 ppm. At those levels, it’s greenhouse effect is much less saturated, and changing it’s concentration does have a measurable effect on temperature.

      • But the high level of difference in temperatures from north to south enabled the very high speed winds that occurred during the coldest periods of the ice age. All around the world there was very high speed winds and much wind scour and accretion of wind blown particles, these aren’t like today’s winds – it’s not just a small change from today. The point is, it was already very cold in north of the world and hence why the wind dropped off the iron so far away. The middle was warm as it almost always is, if CO2 was the most important factor then it wouldn’t have happened. To me it was a massive warm water stratification and a stagnant oceanic conveyor as too much ice limited downward flow of cold water. allowing a massive buildup of heat in the equatorial oceans causing the massive winds speeds seen in this period. When the conveyor started back up, this insanely massive reserve of pent up energy was released – cascading and culminating in the massive melting at the beginning of this interglacial. The very long very cold previous period allowed for this long interglacial and it not being a DO event.

      • If CO2 level dropping below 200 ppm were a powerful cooling force, how did the world ever warm up again?
        The scenario presented seems to be:
        Orbital and tilt changes cause a slight cooling, which increases area covered in snow and ice, which causes gradual further cooling, which causes drought and a shorter growing season, which together cause barren deserts, which release dust into the air, which seeds marine photosynthesis, which reduces atmospheric CO2, which forces further cooling, which increases barreness, which produces…a runaway process until plants starve from CO2 deprevation and all life ends on Earth (except around undersea hot water vents).

        How are we even here to talk about it?

        • They provide no proof as to which came first – the change in CO2 or the cooling. Charts which I have seen from a lecture mentioned on another post all show a further drop in temperature at the end of every ice age, followed by a very sharp rise as the ice age ends. Changes in temperature have always come first where the sequence has been measured, followed by the change in CO2. The solubility of CO2 in water changes dramatically with temperature, and the amount of in in the oceans greatly exceeds the amount in the atmosphere.

      • They are claiming that the drop in atmospheric CO₂ caused the ice age…

        Without taking into account extremely infrared active water vapor’s saturating the minor radiative wavelengths where CO₂ has a little interaction with infrared wavelengths.

        Typical, search for any CO₂ possible interactions then claim/blame that minor CO₂ interaction with everything desired. Thus promoting distant concurrence all of the way past correlation into causation.

        Making their claim specious at best.
        Nor have these researchers accounted for other ice ages preceding the last ice age.

    • Exactly. These Oldenburg researchers say the dust was from “about 20,000 years ago”. But the ice age glacial period had been underway for tens of thousands of years by then. It was already very cold and atmospheric CO2 was already very low!! So the cooling and the low CO2 weren’t caused by the dust. As usual, scientists driven by the need to publish in the corrupt journals had to bend their findings to fit the ruling paradigm, and, also as usual, had to reverse cause and effect in order to get published. We all know that cooling reduces atmospheric CO2 levels. Ralph Ellis and Michael Palmer in the paper cited by Pablo explain how the reduced CO2 levels caused more dust.

      So – the authors of this Nature Communications paper work on the sequence: dust => low CO2=> cold. The actual sequence is: cold => low CO2 => dust.

      They couldn’t have got it any more wrong.

      • Agreed. The glacial period was almost over by the time this dust was deposited. This study does little to advance our knowledge of why glacial periods occur. Two questions for the researchers – since you think the dust went all the way around the world, did you look for it in the southern Atlantic and Indian oceans? You were already surprised at the results so assuming things should be even more frowned upon. Second, your research needs to go back much longer, to see what the iron content of the ocean was during the previous glacial and interglacial cycle. This means deeper core samples.

  1. I wonder if this study would have been undertaken if they hadn’t included “climate change” and the postulation that CO2 controls temperature.

  2. Stopped reading this complete BS after:

    “… promoting CO2 sequestration and thus the glacial cooling of the Earth”

    Which ignores basic chemistry (Henry’s law) and the actual historical CO2 and T data which show that CO2 variations always follow T variations.

  3. As a geochemist (now retired) I would be surprised if this fingerprinting was reliable, especially when a handful of samples are the basis over an area like Russia’s. One would have to bypass the sorting that went on from sources to dstinations, over land, over sea, under sea, then the mixing from potentially several dominant sources. This class of geochemistry seldom gives gifts easily. Too much can be read into results from very low limits of analytical detection on too few samples. But, plus marks for trying, or using a word trendy in IPCC, “ambition”.
    But, after the geochemistry problems come the problems of assumption/ interpretation. Again we see this dedication to the themes of CO2 and temperature, themes that have distorted understanding of the broader aspects of global history. Geoff S

    • You are right Geoff. Just like lakebed pollen samples, never enough samples, never enough locations. I can’t help but think that a lot of bore hole samples that didn’t match some preconceived criterion had to be thrown out due to “evidence of drilling anomaly “. So an interesting hypothesis on CO2 depletion about rusty dust from S. America that doesn’t happen at all anymore….how about ocean current changes over geological time and phytoplankton evolution ?

  4. Great. Now we know how to solve “Global Warming”. Just start dumping iron into the Pacific and let the algae do the rest. Suck about 40 PPM of “anthropogenic” CO2 out of the atmosphere and temperatures should cool right down. Just be careful with how much iron you use lest we end up in another “ice age”. Even as a non-scientist I recognize the tortured logic being tossed out here as “science”.

    • Exactly! If the Climate Scammers really thought there was a Climate Emergency they would be recommending iron fertilization immediately. However it seems only economy destroying solutions are allowed.

  5. “Today, no dust from South America can be detected in the study area. “Global warming has changed the winds and environmental conditions in the source regions,” Struve says, who continues to study the sediment cores. ”

    So Global warming from 20,000 years ago changed the winds.:O

  6. Try again

    Western Argentina now, on a satellite image, looks to be desert. Certainly not green anyway

    Thus, in the millennia leading up to 20,000 yrs ago, ‘somebody’ had been industriously cutting, burning and thereafter running too many grazing animals on what was/is ancient highly weathered soil on what *would* have been a (rain)forest.

    They very effectively triggered a Dust Bowl. As somebody did to create the Sahara we all know and love 6,000 years ago and as Australian aborigines did 30,000 years ago
    The Roaring Forties and Furious Fifties did the rest, moving that dust.
    Just a few days work for them, why the amazement and surprise?

    Blow me down with a feather, with the forest all gone, The Climate Changed

    Amazing stuff innit, the Modern Phlogiston. Completely addles The Climate but most specially, Men’s Brains
    And when I say ‘men’, I really do mean ‘men’

    Boys really. Boys whose sole thinking revolves now revolves around be clever, sensitive & caring in the hope it will get them laid

    The plummeting birth rate suggests that they’ve got that as badly wrong as how they think climate works

    • NW Argentina was strange during the Last Glacial Maximum. Very cold yet humid, causing East Andean glaciers to grow. The pro-glacial meltwater lake beds are visible.

      • I think the US southwest & NW Mexico were similarly wetter. I assume because winter storms traveled much farther south then than now.

    • Peta of Newark, northwest Argentina, cited as the origin of the magic dust, is a high, arid, dusty for sure, barren (except for some habitation around springs) area called “Puna”, which means sick. 20,000 years ago it was the same, maybe with some intermittant small rivers feeding the salars (salt flats, which are the basis for the lithium triangle of today). This study is politically-correct nonsense.

      • Yup. “Puna” is Quechua for mountain sickness. There’s also the Spanish term “soroche” derived from another Quechua word for the effects of altitude hypoxia.

        • Yup, first hand experience with soroche when traveling in and out of LaPaz, Bolivia. Hated that destination, always tried to arrive early to do business in the day, then fly down to Santa Cruz where you could breath and sleep. Airlines changed over time and all landed at El Alto in the evening, forcing one to stay overnight. Things we do for a wage.

          The “salares” are very interesting places, have driven across them in past work, mostly in northern Chile towards the corner with Bolivia. Lots of skeleton towns where mining once took place late 1800’s early 1900’s. Dry as can be, they measure annual rainfall in milimeters and it is mostly mist, not rain as we know it. No surprise at all that dust from there settles over the southern hemisphere oceans. Large extraction of sulphur in the area now with modern machinery.

  7. Glaciation is an energy intensive process. Consider the rate of ice accumulation and how much evaporation is needed. Glaciation is a hemispherical process; not global. All recent Northern Hemisphere glaciations coincided with reducing orbital eccentricity. The evaporation in the Southern Hemisphere outpaced the melting/evaporation of water on land in the Northern Hemisphere so land ice accumulated in the Northern Hemisphere. But the water was evaporated predominantly from ocean surface in the Southern Hemisphere.

    Southern Hemisphere glaciation occurs when orbital eccentricity is low. The Southern Hemisphere gets less insolation when eccentricity is low so it is a little cooler than the more common situation with higher eccentricity.

    It is such nonsense to link any climate impact from atmospheric CO2. Such nonsense needs to be called out. It is laughably naive. There are very powerful negative feedbacks that limit the range of ocean surface temperature and these processes have nothing to do with CO2 or “greenhouse effect” – just bunkum dreamt up by dim wits unable to grasp the basics of atmospheric physics.

  8. It may be a mistake to dismiss this research because the interpretation of the results is biased by the IPCC belief. But the data is real, so how else can it be interpreted?

    • How else can it be interpreted? Please see my comment above. You also need to read thecpaper by Ralph Ellis and Michael Palmer cited by Pablo.

      • Nope. Dust and CO2 are consequences, not causes. Milankovitch forcing and ice build-up reduce temperature, reduce CO2, and increase dust. Mistaking causes and consequences is one of the most common errors in science.

        Milankovitch forcing is primary cause. Reduced temperature and ice build-up are primary consequences and secondary causes. Reduced CO2 and increased dust are secondary consequences.

  9. … BY MEANS OF PLUNGERS AND GRAVITY SOUNDERS.

    What the heck is a gravity sounder and how does it retrieve samples?

    Once again we have something written by the PR department, probably by German speakers. Take everything with a grain of salt.

  10. Wow, they now know what causes ice ages.
    Not.
    The report this article reviews is basically a letter from seekers on a Holy Quest, not science.

  11. I am confused again. The conclusion of the paper was that the iron in the dust caused micro plant life in the oceans to flourish, take CO2 from the atmosphere and therefore cooled the atmosphere. All this happened at the time that the Earth was warming as it moved from a glacial period to an inter-glacial period.

    The evidence that we know contradicts the conclusion. A more logical conclusion would be that the increased microscopic plants in the oceans caused the atmosphere to warm, not cool.

    • DonK

      That’s what I was thinking. 20,000 years ago was not at “the peak”, it was at the end of the last glacial period.

      The main premise of the article fails the basic sniff test. It was however, apparently good enough to fool the project funders which is really all that matters. Another over-simplified explanation of the evil gas that almost anyone can understand, appreciate, and pass on as part of the lore and legend of AWG.

  12. The dust likely came from volcanoes in the Andes and it has traveled on westerly winds around the globe from Argentina & Chile all the way to the Pacific. This is exactly what we saw happen a few years ago when there was a major eruption to the west of Bariloche. The plume was tracked all the way around the globe by satellites.

    Nothing has changed in this behaviour except the ice has retreated since the end of the glaciation thankfully.

  13. So the gradual cooling over the whole glacial interval, just the same as during all the Pleistocene glacial intervals, was just so but the continued cooling at the end, the last glacial maximum, suddenly switched to being caused by CO2?

    Lust like the uniform warming out of the LIA is just so, but the continuation of that warming in the last century suddenly switches to being caused by CO2

    This is just another idi0t story to make every single incidence of past climate change to be caused by CO2.

  14. Analysis of dust on the bottom of the oceans show that dust storms 20,000 years ago were very severe, the likes of which we have no modern examples at all. So we should be glad that we have had 20,000 years of global heating, which has greatly diminished those bygone severe weather events. /s

  15. The problem with this theory is that the CO2 has to be sequestered for it to work. And this requires that the ocean bottom is anoxic.

    The bottom of the Pacific is not anoxic, and hasn’t been since the Cretaceous.

    So, it just won’t work, like most CO2 related “science”.

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