How the Southern Ocean may explain Holocene warming
The oceans are the planet’s most important depository for atmospheric carbon dioxide on time scales of decades to millenia. But the process of locking away greenhouse gas is weakened by activity of the Southern Ocean, so an increase in its activity could explain the mysterious warmth of the past 11,000 years, an international team of researchers reports.
The warmth of that period was stabilized by a gradual rise in global carbon dioxide levels, so understanding the reason for that rise is of great interest, said Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences at Princeton.
Scientists have proposed various hypotheses for that carbon dioxide increase, but its ultimate cause has remained unknown. Now, an international collaboration led by scientists from Princeton and the Max Planck Institute for Chemistry point to an increase in Southern Ocean upwelling. Their research appears in the current issue of the journal Nature Geoscience.
“We think we may have found the answer,” said Sigman. “Increased circulation in the Southern Ocean allowed carbon dioxide to leak into the atmosphere, working to warm the planet.”
Their findings about ocean changes could also have implications for predicting how global warming will affect ocean circulation and how much atmospheric carbon dioxide will rise due to fossil fuel burning.
For years, researchers have known that growth and sinking of phytoplankton pumps carbon dioxide deep into the ocean, a process often referred to as the “biological pump.” The biological pump is driven mostly by the low latitude ocean but is undone closer to the poles, where carbon dioxide is vented back to the atmosphere by the rapid exposure of deep waters to the surface, Sigman said. The worst offender is the Southern Ocean, which surrounds Antarctica. “We often refer to the Southern Ocean as a leak in the biological pump,” Sigman said.
Sigman and his colleagues have found that an increase in the Southern Ocean’s upwelling could be responsible for stabilizing the climate of the Holocene, the period reaching more than 10,000 years before the Industrial Revolution.
Most scientists agree that the Holocene’s warmth was critical to the development of human civilization. The Holocene was an “interglacial period,” one of the rare intervals of warm climate that have occurred over the ice age cycles of the last million years. The retreat of the glaciers opened a more expansive landscape for humans, and the higher concentrations of carbon dioxide in the atmosphere made for more productive agriculture, which allowed people to reduce their hunter-gathering activities and build permanent settlements.
The Holocene differed from other interglacial periods in several key ways, say the researchers. For one, its climate was unusually stable, without the major cooling trend that is typical of the other interglacials. Secondly, the concentration of carbon dioxide in the atmosphere rose about 20 parts per million (ppm), from 260 ppm in the early Holocene to 280 ppm in the late Holocene, whereas carbon dioxide was typically stable or declined over other interglacial periods.
For comparison, since the beginning of industrialization until now, the carbon dioxide concentration in the atmosphere has increased from 280 to more than 400 ppm as a consequence of burning fossil fuels.
“In this context, the 20 ppm increase observed during the Holocene may seem small,” said Sigman. “However, scientists think that this small but significant rise played a key role in preventing progressive cooling over the Holocene, which may have facilitated the development of complex human civilizations.”
In order to study the potential causes of the Holocene carbon dioxide rise, the researchers investigated three types of fossils from several different areas of the Southern Ocean: diatoms and foraminifers, both shelled microorganisms found in the oceans, and deep-sea corals.
CREDIT From left: Ralf Schiebel, Max Planck Institute for Chemistry; Anja Studer, Max Planck Institute for Chemistry; Dann Blackwood, United States Geological Survey
From the nitrogen isotope ratios of the trace organic matter trapped in the mineral walls of these fossils, the scientists were able to reconstruct the evolution of nutrient concentrations in Southern Ocean surface waters over the past 10,000 years.
“The method we used to analyze the fossils is unique and provides a new way to study past changes in ocean conditions,” says Anja Studer, first author of the study, who performed the research while a graduate student working with Sigman’s lab.
The fossil-bound nitrogen isotope measurements indicate that during the Holocene, increasing amounts of water, rich in nutrients and carbon dioxide, welled up from the deep ocean to the surface of the Southern Ocean. While the cause for the increased upwelling is not yet clear, the most likely process appears to be a change in the “Roaring 40s,” a belt of eastward-blowing winds that encircle Antarctica.
Because of the enhanced Southern Ocean upwelling, the biological pump weakened over the Holocene, allowing more carbon dioxide to leak from the deep ocean into the atmosphere and thus possibly explaining the 20 ppm rise in atmospheric carbon dioxide.
“This process is allowing some of that deeply stored carbon dioxide to invade back to the atmosphere,” said Sigman. “We’re essentially punching holes in the membrane of the biological pump.”
The increase in atmospheric carbon dioxide levels over the Holocene worked to counter the tendency for gradual cooling that dominated most previous interglacials. Thus, the new results suggest that the ocean may have been responsible for the “special stability” of the Holocene climate.
The same processes are at work today: The absorption of carbon by the ocean is slowing the rise in atmospheric carbon dioxide produced by fossil fuel burning, and the upwelling of the Southern Ocean is still allowing some of that carbon dioxide to vent back into the atmosphere.
“If the findings from the Holocene can be used to predict how Southern Ocean upwelling will change in the future, it will improve our ability to forecast changes in atmospheric carbon dioxide and thus in global climate,” said Sigman.
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“Increased nutrient supply to the Southern Ocean during the Holocene and its implications for the pre-industrial atmospheric CO2 rise” by Anja Studer, Daniel Sigman, Alfredo Martínez-García, Lena Thöle, Elisabeth Miche, Samuel Jaccard, Jörg Lippold, Alain Mazaud, Xingchen Wang, Laura Robinson, Jess Adkins and Gerald Haug, was published in Nature Geoscience on July 30, 2018, DOI:10.1038/s41561-018-0191-8.
https://www.nature.com/articles/s41561-018-0191-8
Perhaps they should have looked at the solubility curve for CO2 before writing their paper. The solubility at 0 °C is twice that at 20 °C, a slight warming of the oceans, which would be expected at the planet warmed into the inter-glacial would easily account for the increase in CO2 would it not ?.
In historical terms a rise of 20 ppm is negligible given that atmospheric CO2 has ranged between 180 and >6000 ppm. For 70% of the last 600 million years it has been over 1000 ppm without any adverse effect. 200 ppm change is nothing
As if we needed more evidence that the academic natural sciences are in the Dark Ages. The stupidity on display in this study, it’s too much for words.
so lets see..
today there is more upwelling of CO2 near Antarctica.
That must be why Antarctica is warming ,right?
Loe
If CO2 up-welling increased near Antarctica during the sampling station era, it would show in the CO2 trends from those stations on Antarctica. They would be higher than those of New Zealand and Tasmania. They are not.
Leo, not Loe
This started with the same “…CO2 done warmed the world…” which has been so thoroughly disproven, I couldn’t read any more of it! GIGO, and they didn’t even have to use a computer to do it!
http://jo.nova.s3.amazonaws.com/graph/paleo/holocene/gisp-holocene-temperatures-greenland-co2.gif
Thought the world had cooled over the past 11,000yrs
To protect oneself from pointless distraction and useless mental pain, one thing is necessary with these “look-what-the-media-said-about-this-research” type of announcements. Skip what the media said. Try to avoid reading even a single word. Go straight to the actual paper’s abstract. Do not pass go. Do not collect 200. Just go straight to the abstract. At all costs ignore the media blather.
The research makes reasonable sense. Why was CO2 rising during the Holocene while temperatures were generally falling? Non human source of rising CO2 (oceanic) is acknowledged. The horror. The horror. But it’s fine.
This is completely nonsense.
They have their CO2 emissions upside down: the largest ocean upwelling is off the coast of Chile and Peru in the East Pacific. It is there that most of the CO2 emissions from warming up deep ocean waters is. That is measured as a strong pCO2 of the ocean waters of around 750 μatm. As the atmosphere is currently around 400 μatm (~ppmv), then the CO2 flux is out of the oceans. Near the poles, the ocean’s pCO2 is around 150 μatm, thus the sinking ocean waters take a lot of CO2 out of the atmosphere into the deep. That is as well the case for the Southern ocean as for the N.E. Atlantic.
Even when in pre-industrial times the atmospheric CO2 levels were lower, still the high-latitude oceans were CO2 sinks, not sources…
See the maps at: https://www.pmel.noaa.gov/pubs/outstand/feel2331/maps.shtml
Good comments, thank you Ferdinand.
Seems like another sneaky way to reinforce the AGW fraud, especially sneaky if skeptics support it.
Finally, a paper that highlights the absurdity about co2 levels. At 20 ppm/v keeps us from falling into a deeper ice age, while an additional 126 ppm/v does, well practically nothing. If co2 was doing something besides making plants healthier.
What should have happened at 300 ppm/v or (the horror) when it was 350 ppm/v ?
How does AGW rationalize this? So far 126 ppm/v raises the temp, according to AGW supporters by 0.8 C. Just going along with the framework. So, it’ll take 157 ppm/v to raise the temp by 1 C. Then that 20 ppm/v raises the temp by 0.12 C ?
Then if we used the other way where 280 ppm/v rose temp by 33 C ( from the blackbody) then it’s 8.48 ppm/v that raises the temp by 1 C. So, I can see that, you’d get a 2.5 C increase. But then what about the 126 ppm/v increase??? The temperature has clearly not gone up 14.8 C .
Biggest offender I see are people trying to justify co2 as a temperature regulator.
The facts:
For the last 8000 years of the Holocene CO2 rises by 20 ppm while temperatures steadily fall.
The reporting:
“Leaking” CO2 (that must be the 20ppm rise they’re talking about) warms the planet.
Curious kind of warming that causes temperatures to fall.
I read someone’s PhD dissertation where his research appeared to uncover evidence of a shutdown of Pacific circulation during the last glacial which resulted in a large pool of liquid CO2 forming in the Southeastern Pacific on the ocean bottom in this stagnant location. Once the circulation started again, this CO2 was dissolved in the moving waters and eventually vented to the atmosphere during upwelling.
I found that dissertation and it is fascinating reading.
https://deepblue.lib.umich.edu/bitstream/handle/2027.42/62273/waddelin_1.pdf;jsessionid=C4661A63D2042CE08ADFB08D97538465?sequence=1
The warmists forget that when the ice caps were some thousands of meters thick over Canada (Laurentia) and Scandinavia (18 kY ago), the sea level was down by 120 m. This means that the pressure on the seafloor was 12 bars less. This caused a lot of gases, including CH4 to seep out into the atmosphere. There was also a lot of dust in the atmosphere, which probably decreased the albedo of the ice. However, after the first warming, between 15 kY and 12 kY ago, there was a brutal set-back with the Younger Dryas cold spell, which only took about 50 years to develop.
The ice was, however, finally gone by about 9 kY ago. Then came the optimum period of the Holocene, when the temperature was about +4 C higher than today (at 5 – 4 kY ago). There were no glaciers in Norway at that time, and the sea-level was bout 6 m higher than today….
Nobody knows, however, why and how these temperatures came about. The main conlcusion is that: As long as we cannot figure out what happened here, -why bother with trying to explain AGW… ?
This idea is total and complete rubbish.