A new study published by researchers at the University of Hawai‘i (UH) at Mānoa sheds light on the critical role of iron in Earth’s climate history, revealing how its sources in the South Pacific Ocean have shifted over the past 93 million years. This groundbreaking research, based on the analysis of deep-sea sediment cores, provides crucial insights into the interplay between iron, marine life, and atmospheric carbon dioxide levels.
Iron is a vital nutrient for marine life and plays a significant role in regulating atmospheric carbon dioxide by influencing the growth of phytoplankton, which absorb carbon dioxide. Although the importance of iron today is well-established, researchers have a limited understanding of how past iron availability may have shaped the marine ecosystem.
To investigate the long-term history of oceanic iron, the researchers meticulously analyzed iron isotopes in three deep-sea sediment cores from the South Pacific, far removed from continental influences.
“Over the past 93 million years, we found that five primary sources of iron have influenced the South Pacific Ocean: dust, iron from far off ocean sources, two distinct hydrothermal sources, and a volcanic ash,” explained Logan Tegler, the lead author and oceanography postdoctoral researcher in the UH Mānoa School of Ocean and Earth Science and Technology. “These sources shifted over time as the sites gradually migrated away from mid-ocean ridges.”
The study revealed an evolution in iron supply: initially, hydrothermal sources were the dominant source, but dust gradually took over, becoming the primary contributor around 30 million years ago.
Iron’s influence on the ecosystem, carbon removal
“Understanding this historical context helps us comprehend how iron has shaped ecosystems,” said Tegler. “It also raises questions about how the iron cycle might have favored certain microbes over others—an ecosystem with persistently low iron could favor microbes adapted to survive under iron-limited conditions, such as diatoms.”
In many regions of the Pacific Ocean, iron availability limits the growth of phytoplankton, thereby limiting the amount of carbon dioxide removed from the atmosphere.
“Modern dust deposition in the South Pacific is extremely low,” said Tegler. “However, our findings surprisingly suggest that the South Pacific is currently receiving more dust than it has at any point in the last 90 million years, which is remarkable given its current reputation as an iron poor region!”
This study sheds light on iron cycling across the broader Pacific basin and enhances understanding of how essential nutrients like iron shape ocean ecosystems and climate over millions of years.
“As human activities increase iron input to the oceans through industrial emissions and biomass burning, understanding past perturbations of the iron cycle is crucial for predicting and mitigating adverse effects,” added Tegler.
Journal
Paleoceanography and Paleoclimatology DOI 10.1029/2025PA005149
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
One more piece of an extremely complex puzzle.
The Earth is amazing item. I can imagine vast numbers of other interesting planets out there. I think if I was a “youngin agin” I’d study astronomy with a specialty in planetary studies. The planetary research being done today in fantastic.
You might find it less interesting than you imagine. An awful lot of modern astronomy revolves around “modeling.” At least that is what I gathered from attending I don’t know how many thesis defenses and seminars over in the astronomy department during my academic career….
That was one of the things that pushed me away from getting a second, physics, major and leaving it as just mathematics as an undergrad.
As I sat in my astrophysics courses I had mental image of studying physics as something different than mixing and matching the simulations of internal solar layers and matching them to externally measured phenomena and trying to find a mixture that matched the externally measured values.
Now… I see the value of building a model of something, even if is something less formal and in my head, but I just couldn’t shake the feeling that what I was doing wasn’t the ‘physics’ I read about in all of the biographies about science and scientists.
I guess, maybe if somebody had been able to demonstrate to me that that was really what ‘natural philosophy’ really was, well, maybe I’d have thought longer about getting that major.
However, our findings surprisingly suggest that the South Pacific is currently receiving more dust than it has at any point in the last 90 million years.
Perhaps Australian iron mining is the cause. That is dust being blow off the mine pits?
When CO2 levels drop, as they have been for the last 90 million years, the number of plants also drops. Plants hold down soil, making it more difficult for wind to carry it away as dust.
As recently as 300 years ago, atmospheric CO2 never exceeded 280 ppm. Today, it’s 423 ppm, and steadily rising. Isotopic analysis shows all of the 50% increase in atmospheric co2 concentration since 1750 was produced by the burning of fossil fuels, currently being emitted at the rate of 40 gigatonnes annually. Analysis of the increased atmospheric greenhouse effect shows that about 80% of post industrial warming is due to these fossil fuel emissions
This seems not quite credible because the last glacial was very dusty because the climate was exceptionally dry. In fact, the atmospheric dust load at that time is considered a possible factor bringing the Earth out of the ice age. More complexity…
‘In fact, the atmospheric dust load at that time is considered a possible factor bringing the Earth out of the ice age.’
I always thought that was the most plausible mechanism. Even after the Milankovich cycle(s) had swung back towards greater solar isolation, there would still likely have been an issue with high albedo given the extent of hemispherical glaciation. It seems logical, then, that the biggest offset to this would have been a decrease in albedo driven by dust from exposed sea floors and deserts, which would have expanded greatly when moisture was locked up in ice sheets and CO2 levels were approaching marginal levels for plant life, particularly at altitude.
mysteries upon mysteries! which makes it fascinating
Story tip:
The cost of “free” green energy just doubled. UN chief says every $ spent on renewable energy must be matched by a $ on infrastructure to avoid Spanish style blackouts.
“Investments in the right infrastructure are not keeping up,” said António Guterres, head of the United Nations, in a July speech. “That ratio should be one to one.”
https://www.bloomberg.com/features/2025-bottlenecks-blackouts-grid-stability-solar-wind/
Guterres is an empty suit. Could not get a job in the private sector
Offshore wind, producing electricity at 15 c/kWh (after 50% subsidies), plus 11 c/kWh to reflect the full cost of electricity, FCOE, owned/controlled by European governments and companies, would be a serious disadvantage for the US regarding environmental impact, national security, economic competitiveness, and sovereignty
HIGH COST/kWh OF W/S SYSTEMS FOISTED ONTO A BRAINWASHED PUBLIC
https://www.windtaskforce.org/profiles/blogs/high-cost-kwh-of-w-s-systems-foisted-onto-a-brainwashed-public-1
According to AJ, it’s not fair to add the cost of upgrading the grid to handle wind and solar, to wind and solar.
Upgrading the grid is just 2 c/kWh of the 11 c/kWh needed to reflect the full cost of energy, FCOE.
FCOE = 30 c/kWh + 11 c/kWh = 41 c/kWh, without any subsidies
FCOE = 15 c/kWh + 11 c/kWh = 26 c/kWh, with 50% subsidies
Uh oh. I recall some time ago there were some buzz about lowering atmospheric CO2 levels by seeding oceans with iron filings to cause massive algae blooms. Apparently, it’s back on the menu…
https://www.whoi.edu/ocean-learning-hub/ocean-topics/climate-weather/ocean-based-climate-solutions/iron-fertilization/
The ocean absorbs anthropogenic CO2 anyhow. Unlike what “climate scientists” like to claim, the huge DIC ocean reservoir (~39,000GtC) is continuously exchanging with the atmosphere, a far smaller reservoir with only 900GtC today, and ~600GtC pre-industrial.
Even in the deep ocean the C14 age is only about 2000 years. So that is 39,000GtC moving out into the atmosphere, and back into the ocean every 2000 years, at a rate of >39000/2000 = 19.5GtC annually.
Curious, me knowing little about the ocean- is there a formula such that if you double the CO2 in the ocean, how much would the % of CO2 in the atmosphere increase from the outflow from the ocean? Over time of course.
How would you double CO2aq? I mean I am not questioning your godly powers, it is just a chemical thing.
DIC (dissolved inorganic carbon) comes in three flavours..
90% HCO3
9% CO3
<1% CO2
If you would just double CO2, it would almost instantly, or least in a very short time, reduce CO3 a little, increase HCO3 levels, and otherwise disappear almost entirely.
There was a paper, no longer available, at https://shalemag.com/the-physics-chemistry-of-carbon-dioxide-formation/ (really, no longer available) that tried to demonstrate that the oceanic CO2 dynamic was greatly facilitated by the known relationship between CO2 absorption and releases from seawater as the oceans either cooled (absorbed) or heated up (emitted) CO2. The paper even contained a heat map that showed the areas of CO2 absorption and release from the oceans in the cooler and warmer regions in the oceans including a discussion about the mechanics and speed with which this exchange takes place.
This process was mediated by the chemicals in the ocean that either buffered the rising acidity and removed it from the seawater so it didn’t become too acidic, including the chemistry.
He didn’t do any C14 dating to discuss the possible cycles and their lengths but the paper made a lot of sense.
Sorry, I don’t have a copy of the paper, I’ve looked for it and couldn’t find it again. But, on a fairly careful read of paper I thought it was one of the better discussions of the mechanism of CO2 exchange in the oceans. It sure would be nice to get something from these sites other than a 404 error when I know the page was there before.
John Martin became an original researcher and proponent of the importance of iron to oceanic life. At the time (1989) it was supposed generally that phosphorus was the life limiting ingredient. Martin, instead insisted that measurements of iron in the ocean were wrong (too rich in iron) because iron was a common contaminant in every measurement effort. He got around to finally soaking his sample bottles (plastic) in nitric acid for long periods to leech out the iron contamination left by iron molds used in the bottle manufacture. His tireless efforts showed iron to be a contender for life-limiting component.
In 1989 he proposed experiments to fertilize the ocean with iron. Discover Magazine, which I wasn’t especially fond of, wrote an article regarding Martin’s research and his proposed experiments. I was pretty excited about such a prospect because I was then, and still am, a proponent of making historical sciences like Geology more like experimental science. I wrote a letter to the editor pointing out that Earth does experiments like this on a periodic basis (volcanoes, major dust storms, etc) anyway, but these experiments go unmeasured, thus unevaluated in any useful way.
By weird coincidence in the Letters to the Editor section next to my note, Sen. Al Gore (who I’d never heard much about before) weighted in with his trademark blather that such experiments were too dangerous to consider. It’s the only time in my life that I have been on the “same page” as Al Gore.
Too funny! I don’t suppose Gore also weighed in on the dangers of listening to Marxist misanthropic malthusians and de-industrializing the West.
Too dangerous. That’s simple minded. Of course it would have to be done intelligently. Apparently Gore can’t grasp that or doesn’t want to. It seems that he doesn’t consider installing ruinables on a large scale to be dangerous in any way.
Lots of dust blowing around, hard on hurricanes? Got to attribute it to something? Also–
Walsh, J. J. and K. A. Steidinger. 2001. Saharan dust and Florida red tides: The cyanophyte connection. J. Geophys. Res. 106(C6):11597-11612.
https://doi.org/10.1029/1999JC000123
Iron stimulates the blue-green (old term) which fixes nitrogen from the air, supplies it to red-tide organism. According to some nitrogen is already one of our over-fertilized ocean demons but it’s a long way from being a pig-sty. Variable ligand experiments maybe?
growth of phytoplankton, which absorb carbon dioxide.
No CO2, no phytoplankton
The CO2 of fossil and other sources released to the atmosphere, of which 50% is absorbed by oceans, immediately produces phytoplankton, especially in colder waters (reverse solubility), the reason whales go north to feed and have their babies.
Iron is a vital nutrient for marine life and plays a significant role in regulating atmospheric carbon dioxide by influencing the growth of phytoplankton,
What about fish, they exhale a lot of CO2.. and they kind of need iron.
The small ones get the iron they need by eating phytoplankton.
The bigger ones get the iron by eating the fish that eat phytoplankton.
And they respire – a lot
Shush…don’t give the remaining whale hunters an argument for hunting whales in the name of reducing CO2 emissions. sarc
Story tip
Dale Vince – One of Labour’s Biggest Donors – Has Contracts Worth £3.5 Million with London Mayor Sadiq Khan’s City Hall
Reform UK’s Zia Yusuf said: “The fact one of Labour’s biggest donors, Dale Vince’s Ecotricity, has been handed £3.5 million of taxpayer money from Sadiq Khan’s Greater London Authority in the last five years will enrage taxpayers.”
https://dailysceptic.org/2025/08/26/dale-vince-one-of-labours-biggest-donors-has-contracts-worth-3-5-million-with-london-mayor-sadiq-khans-city-hall/
OT Story Tip:
23 Republican attorneys general urge EPA to cut climate group funding | Fox News
Why would ‘industrial emissions’ of iron be high?
I’d consider muddy rivers flowing into the seas as the major source of terrestrial iron into the ocean systems. Volcanics poop out mainly basalt or high magnesium/iron rock. In the high pH marine environment, iron is highly mobile. 3/4th of Earth’s volcanoes are submarine volcanoes … virtually all volcanic output is going to end up in the seas, considering most terrestrial volcanism outputs are quickly transported to the seas.
According to GROK, about 180 million tons of Sahara dust ends up in the ocean every year. How much of that is iron? —about 5%. So about ten million tons per year.
Since the introduction of ships with iron and steel construction in the late nineteenth century, many million tons of passenger, cargo and military ships have sunk to the bottom of the oceans. Do these rusting ships contribute any iron to the oceans?
Currents that run in the deep oceans are slow, so it will take a long time before the iron from these wrecks will be able to move from the deeps to the surface.
The fires in Australia some years ago produced a plume of iron rich smoke reputed to have stimulate phytoplankton such that 80% of the CO2 was absorbed between NZ and south America within weeks.
Speaking of iron: Under various names there are clubs that show and demonstrate early (old) farm and ranch machinery. For example in mid-September the Kittitas Valle Early Iron Club will have a “Threshing Bee.”
I last participated in such a thing about 1951 on an uncle’s farm.
What is not reported is the massive amount of “old iron” out behind the barns and in the back lots of the ranches. Old cars and trucks find their way to wrecking yards and are partially repurposed or torn apart and sent to smelters.
See: (1) Junk yards; and (2) Shredding Machines
Leaving more food for terrestrial plants, is that it?
All part of the grand tapestry of the universe.