We have in the past made fun of ideas to fertilize the ocean with iron dumped by ships to reduce carbon dioxide. The last experiment failed miserably. Meanwhile nature says, “hold my beer.” From Frontiers in Marine Science and Florida State University comes this press release.
Oceanic life found to be thriving thanks to Saharan dust blown from thousands of kilometers away
The further dust-bound iron is blown from the Sahara, the more it becomes available for life through atmospheric reactions.
Iron is a micronutrient indispensable for life, enabling processes such as respiration, photosynthesis, and DNA synthesis. Iron availability is often a limiting resource in today’s oceans, which means that increasing the flow of iron into them can increase the amount of carbon fixed by phytoplankton, with consequences for the global climate.
Iron ends up in oceans and terrestrial ecosystems through rivers, melting glaciers, hydrothermal activity, and especially wind. But not all its chemical forms are ‘bioreactive’, that is, available for organisms to take up from their environment.
“Here we show that iron bound to dust from the Sahara blown westward over the Atlantic has properties that change with the distance traveled: the greater this distance, the more bioreactive the iron,” said Dr Jeremy Owens, an associate professor at Florida State University and a co-author on a new study in Frontiers in Marine Science.
“This relationship suggests that chemical processes in the atmosphere convert less bioreactive iron to more accessible forms.”
The core of the matter
Owens and colleagues measured the amounts of bioreactive and total iron in drill cores from the bottom of the Atlantic Ocean, collected by the International Ocean Discovery Program (IODP) and its earlier versions. IODP aims to improve our understanding of changing climate and oceanic conditions, geological processes, and the origin of life. The researchers selected four cores, based on their distance from the so-called Sahara-Sahel Dust Corridor. The latter ranges from Mauritania to Chad and is known to be an important source of dust-bound iron for downwind areas.
The two cores closest to this corridor were collected approximately 200km and 500km west of northwestern Mauritania, a third in the mid-Atlantic, and the fourth approximately 500km to the east of Florida. The authors studied the upper 60 to 200 meters of these cores, reflecting deposits over to the last 120,000 years – the time since the previous interglacial.
They measured the total iron concentrations along these cores, as well as concentrations of iron isotopes with a plasma-mass spectrometer. These isotope data were consistent with dust from the Sahara.
They then used a suite of chemical reactions to reveal the fractions of total iron present in the sediments in the form of iron carbonate, goethite, hematite, magnetite, and pyrite. The iron in these minerals, while not bioreactive, likely formed from more bioreactive forms through geochemical processes on the seafloor.
“Rather than focusing on the total iron content as previous studies had done, we measured iron that can dissolve easily in the ocean, and which can be accessed by marine organisms for their metabolic pathways,” said Owens.
“Only a fraction of total iron in sediment is bioavailable, but that fraction could change during transport of the iron away from its original source. We aimed to explore those relationships.”
Blowing in the wind
The results showed that the proportion of bioreactive iron was lower in the westernmost cores than in the easternmost ones. This implied that a correspondingly greater proportion of bioreactive iron had been lost from the dust and presumably been used by organisms in the water column, so that it had never reached the sediments at the bottom.
“Our results suggest that during long-distance atmospheric transport, the mineral properties of originally non-bioreactive dust-bound iron change, making it more bioreactive. This iron then gets taken up by phytoplankton, before it can reach the bottom,” said Dr Timothy Lyons, a professor at the University of California at Riverside and the study’s final author.
“We conclude that dust that reaches regions like the Amazonian basin and the Bahamas may contain iron that is particularly soluble and available to life, thanks to the great distance from North Africa, and thus a longer exposure to atmospheric chemical processes,” said Lyons.
“The transported iron seems to be stimulating biological processes much in the same way that iron fertilization can impact life in the oceans and on continents. This study is a proof of concept confirming that iron-bound dust can have a major impact on life at vast distances from its source.”
🙂…….
Question.
If the iron sampled from the cores is what settled to the bottom, then surely that iron WASN’T taken up by life.
Why not sample the living organisms in the ocean and see what iron they’ve got in them.
Great question. Two possible answers, neither doubting the new study observational data posted by AW to his most excellent WUWT.
First, more dust will be available than phytoplankton at the beginning of fertilizing a ‘bloom’. So some is ‘wasted’ and settles to an ocean core. Timing.
Second, they got soluble availability right, but not bioavailability. See research comment below just posted for an explanation of the subtle iron distinctions. Translation, physical chemistry does not necessarily translate directly into organic chemistry.
Wild guess based on no knowledge, but isn’t it possible iron that settled to the bottom- might get disturbed during severe storms and then become available to some organisms? At least in some places.
Sorry, I wrote this question before I saw Rud’s very informative post below.
I think it’s well known, no Amazonas Rainforest without dust from Sahara.
2010
https://www.nature.com/articles/news.2010.396
2015
https://www.climatecentral.org/news/sahara-dust-amazon-rainforest-nasa-18708
2017
https://acp.copernicus.org/articles/17/2673/2017/
Yup.
Three deeply interesting (well, to me) iron corollaries to AW’s excellent post.
First, for people dietary iron comes in two ‘forms’, heme and non-heme. Heme comes from iron rich meat foods like liver and red meat. It is preselected for blood hemoglobin use by the source animal metabolism. Non-heme comes mostly from iron rich vegetables like spinach, but is not preselected, so is much less bio-available. Translation: a lot of spinach needed to equal a little steak.
Second, Ocean iron fertilization efficacy depends not just on dust iron amount, but also on dust iron ‘quality’, as this new paper shows. Now in lab experiments with ocean phytoplankton, the two key ‘quality’ uptake rate drivers are solubility (sure=>ocean water quantity) and bioavailability (like heme for humans). Turns out (I just quick googled several research papers) that BOTH are enhanced the longer atmospheric iron laden dust is exposed to atmospheric ‘acidic pollution’. Explaining the new paper result. After cleaning up SO2, the biggest atmospheric ‘acidic pollutant’ is CO2, which is why rainwater has a pH of about 4.5 from carbonic acid and partly why Everglades freshwater is actually acidic. SO, the higher atmospheric CO2 is, the more effective atmospheric dust is at fertilizing phytoplankton and sequestering ocean CO2 as calcium carbonate. A fascinating and biggish negative feedback nowhere in any CMIP6 climate model.
Third, what the Sahara does for ‘fertilizing’ the mid Atlantic, the Australian interior desert does for the entire global Southern ocean thanks to the Antarctic circumpolar current. Explaining its very high krill fertility. (Krill feed on phytoplankton. Everything from penguins to Antarctic Toothfish [aka Chilean Seabass] to balleen whales feed mainly on krill or the small baitfish like Antarctic silverfish (herring genus) that feed on krill.)
Everything I see says rain water is typically 5-5.6 weakly acidic
Sorry. You are of course right about pure rain. At least I qualified my statement by ‘partly’. I am a Florida centric Everglades guy. The rain/ Everglades difference is why the Great Dismal swamp water is ~pH 4.5 in summer. Also why peat bogs in Europe have preserved human remains for thousands of years.
I used to leave a pH meter probe in a cup of distilled water to keep the membrane from drying out after a measurement. when i would come in the morning to the sample room, the pH would always be at 5.5. I know, this was a no buffer situation, but that is the accepted pH in a no buffer/no dissolved solids situation.
Mr. Istvan: Thanks for solid comment as usual. “a lot of spinach needed to equal a little steak.” It’s a wonder Popeye didn’t eat steak, an obvious misinformation campaign by Big Spinach.
“SO, the higher atmospheric CO2 is, the more effective atmospheric dust is at fertilizing phytoplankton and sequestering ocean CO2 as calcium carbonate.”
This is the second major Earth influence that is not included in climate models that I’ve read today.
The other one refers to H₂O energy inter cell poleward transport.
May I suggest that along with research on tap in the reference section we keep things like important drivers/factors missing in climate models there too?
And perhaps other juicy tidbits? To be identified?
More wind more Fe in oceans, More dry desert more Fe in oceans, more Fe in oceans more marine life etc.
I still see Fe fertilization as a good option for marine farming on a regional broad acre basis because it is the right type of fish feed not soy etc. Plus the side benefit of consuming the FF CO2 from the atmosphere, clearly also impacting the pH of the ocean should you vex over this.
Problem with fish farming is, fish are by definition penned in. So they need feed they cannot free range find. Now their feed could be grown and harvested in open oceans via fertilization. Just like on my Wisconsin dairy farm—we fertilize the alfalfa feed crop, not the cows.
As Amazon and Sahara are in discussion it’s maybe interesting to know, that the Amazon in times Africa and South America were one continent, the Amazon just was flowing in the other direction with the probably source in Tschad, eastern Sahara.
I thought the Sahara was green and wet for much of the last 120,000 years and only became a vast desert about 5,000 years ago. Surely it was not a major source of dust for the Atlantic for much of the period covered by the cores studied.
I read the Andes were once a big source
120,000 tears is a very long time and natural climate variation undoubtedly led to drier intervals conducive to dust development and aerial transport.
Future alarmist headline: “Greening Sahara Destroying Mid Atlantic Biome”.
Oh the irony.
Protect the deserts !!
😉
gotta save the scorpions and fire ants!
https://www.sciencedirect.com/science/article/pii/S0048969721058538
This a fantastic account of the impact of Fe on the oceans as a consequence of fires.
It literally makes the case for fires being net negative for planetary CO2 balance.
Its an interesting discussion when you suggest that the use of robust fire fighting is a direct contributor to CO2 levels rising, I think its supportable.
But clearly Fe and other trace elements are critical to phytoplankton growth and the ocean based food chain.
One further point that has bugged me is the idea that maybe industrial fishing and the consequent removal of Fe from the oceans has contributed to the imbalance. The basis is the small quantity removed prior to fishing or is this simply not material.
A 2015 article regarding Australia’s dust storms and phytoplankton:
https://theconversation.com/how-australias-biggest-dust-storm-went-on-to-green-the-ocean-47695
“Our research shows the two dust storms that traversed the south-east coast of Australia caused a widespread spike in phytoplankton biomass in the Tasman Sea.”
Interestingly, they state (my bold):
“One proposed way of dealing with climate change includes fertilising the oceans with iron. This “geoengineering” would encourage the growth of microscopic plants – phytoplankton – which, if growing vigorously enough, remove carbon dioxide from the atmosphere.”
Who knew phytoplankton live in the air and die in the oceans?
Also, it comes from the Gobi, and in smaller amounts from the deserts of the N. America Southwest.
I’ll just drop this here as a STORY TIP for the mods –
https://cliffmass.blogspot.com/2024/09/if-you-care-about-environment-and-worry.html#comment-form
Dr Mass explains in detail the fundamental faults of politicized “climate action” policies.
Current situational data gets totally ignored when politicians, activists and bureaucrats have a “crisis” agenda to inflict.
He still says it’s a serious problem, just not “existential”. I fail to see much of a difference. It’s going to be politicized no matter what. You can’t get that genie back into the bottle, Dr. Mass.
Cliff’s take on regional warming / centennial changes in regional climates resonates with me because he considers what substantial physical changes have been carried out to regional landscapes as a result of human activities – e.g. broadscale land clearing, asphalting roads and roofs, concrete buildings, etc, etc, etc.
For all this, he ascribes a ~ 1 degree F impact on prevailing temps in the US Pacific North-West states over the last 100 years.
There is NO CLIMATE CRISIS!!!!
“I’m simply saying that life, uh… finds a way.”
— Dr. Ian Malcolm
I really understood that when I read that some life is found in rocks hundreds of feet beneath the surface. Some of it extremely old. Certainly that life will survive even a full scale nuclear war.
Yeah, but probably not us…..
Mine wastes of all kinds, are almost always very rich in iron and other elements which are essential to life. On land, these mine wastes often represent toxic hazards. Diluted, and slowly ‘added’ to seawater on long voyages of the tens of thousands of vessels plying the ocean, they represent a major source of micronutrients. Two problems would be solved… getting rid of mine wastes (even ‘so called toxic wastes’… no longer toxic if well-diluted) and adding nutrients to seawater. Everyone benefits. Alaskan volcanos that spewed iron rich ash into the Aleutian sea, are well known to benefit the Salmon population, and other life forms in that area. ‘Smokers’ which add volcanic heat and ’emissions’ to oceans, always ‘teem’ with life.
“This implied that … and presumably been used by organisms in the water column, so that it had never reached the sediments at the bottom.”
Did they measure at 4 points then make a map of the entire Atlantic Ocean based on only that data? I love the paper but the map requires a movie-like suspension of disbelief. Oh. I guess its okay if they used a computer.
They say not all its chemical forms are ‘bioreactive’ without bothering to say which are and which aren’t. Their paper is very vague on this point. Can anyone fill in the missing information?
Also, only 4 test locations? They can’t be serious!
“Owens and colleagues measured the amounts of bioreactive and total iron in drill cores from the bottom of the Atlantic Ocean”
Boreholes 1062 & 1063 are in the Sargasso Sea area.
Apparently, active iron enrichment for many millions of years.