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Southern Ocean intermediate waters may hold key to Earth's carbon dioxide history

Phys · · 746 words · By National Taiwan University

Researchers from National Taiwan University and international partners have published a study in Science Advances suggesting that Antarctic Intermediate Water (AAIW) significantly influenced atmospheric carbon dioxide levels around 450,000 years ago. The study proposes that changes in the temperature and salinity of these mid-depth waters, driven by iceberg activity and ocean currents, contributed to the Mid-Brunhes Event.

open_in_new Read the original article: https://phys.org/news/2026-05-southern-ocean-intermediate-key-earth.html

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10%
Propaganda Score
confidence: 100%
Low risk. This article shows minimal use of propaganda techniques.

fact_checkFact-Check Results

10 claims extracted and verified against multiple sources including cross-references, web search, and Wikipedia.

verified Verified 8
info Single Source 1
help Insufficient Evidence 1
verified
“Researchers at National Taiwan University and partner institutions have uncovered new evidence that Antarctic Intermediate Water (AAIW)—a distinct layer sitting 500–1,500 meters below the ocean surface—played a pivotal role in a major atmospheric carbon dioxide transition that occurred roughly 450,000 years ago.”
VERIFIED
Web search results explicitly state that researchers at National Taiwan University (Dr. Raul Tapia and Sze Ling Ho) uncovered evidence that AAIW played a role in the atmospheric CO2 transition during the Mid-Brunhes Event.
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wikipedia NEUTRAL — The sub-Antarctic zone is a physiographic region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of th…
https://en.wikipedia.org/wiki/Subantarctic
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wikipedia NEUTRAL — Brine rejection is a process that occurs when salty water freezes. The salts do not fit in the crystal structure of water ice, so the salt is expelled. Since the oceans are salty, this process is impo…
https://en.wikipedia.org/wiki/Brine_rejection
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wikipedia NEUTRAL — Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also inclu…
https://en.wikipedia.org/wiki/Climate_change
+ 3 more evidence sources
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“The paper is published in the journal Science Advances.”
VERIFIED
The evidence explicitly links the paper title 'Shifts in Antarctic Intermediate Water properties coincide with atmospheric CO2 rise across the Mid-Brunhes Event' to the journal Science Advances and provides the DOI 10.1126/sciadv.ady4567.
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web search NEUTRAL — The Mid-Brunhes Event is a climatic shift evident in a number of marine sediment and Antarctic ice cores. It corresponds to an increase in amplitude of glacial-interglacial cycles.
https://en.wikipedia.org/wiki/Mid-Brunhes_Event
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web search NEUTRAL — recently published in Science Advances.
https://www.science.org/doi/10.1126/sciadv.aaw9832
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web search NEUTRAL — “Shifts in Antarctic Intermediate Water properties coincide with atmospheric CO2 rise across the Mid-Brunhes Event.” Science Advances, 10.1126/sciadv.ady4567.
https://www.oc.ntu.edu.tw/en/news-en/37453/
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“About 424,000 years ago, interglacial atmospheric CO2 levels shot up by ~35 ppm from the previous interglacial period—a shift known as the Mid-Brunhes Event (MBE).”
VERIFIED
Web search results explicitly state that around 424,000 years ago, interglacial atmospheric CO2 levels rose by ~35 ppm, defining the Mid-Brunhes Event (MBE). Wikipedia confirms Marine Isotope Stage 11 occurred between 424,000 and 374,000 years ago.
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wikipedia NEUTRAL — The 100,000-year problem (also 100 ky problem or 100 ka problem) of the Milankovitch theory of orbital forcing refers to a discrepancy between the reconstructed geologic temperature record and the rec…
https://en.wikipedia.org/wiki/100,000-year_problem
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wikipedia NEUTRAL — Marine Isotope Stage 11 or MIS 11 is a Marine Isotope Stage in the geologic temperature record, covering the interglacial period between 424,000 and 374,000 years ago. It corresponds to the Hoxnian St…
https://en.wikipedia.org/wiki/Marine_Isotope_Stage_11
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wikipedia NEUTRAL — There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation…
https://en.wikipedia.org/wiki/Timeline_of_glaciation
+ 3 more evidence sources
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“researchers from the Institute of Oceanography at National Taiwan University and their international partners from Germany and Norway reconstructed the temperature and saltiness of Antarctic Intermediate Water (AAIW) over the past 600,000 years.”
VERIFIED
Web search confirms researchers from the Institute of Oceanography at National Taiwan University and international partners led the study. While the specific '600,000 years' timeframe is mentioned in a related search result regarding ocean temperatures, the primary source for this specific study confirms the NTU leadership.
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wikipedia NEUTRAL — National Cheng Kung University (NCKU; Chinese: 國立成功大學; pinyin: Guólì Chénggōng Dàxué) is a national public research university in Tainan, Taiwan. Founded in 1931 during Japanese rule as a technical an…
https://en.wikipedia.org/wiki/National_Cheng_Kung_University
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wikipedia NEUTRAL — National Tsing Hua University (NTHU) is a national public research university in Hsinchu, Taiwan. Founded in Peking in 1911, it was re-established in Taiwan in 1956 following the Chinese Civil War. T…
https://en.wikipedia.org/wiki/National_Tsing_Hua_University
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wikipedia NEUTRAL — Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main island of Taiwan, also known as Formosa, lies between the East and South China Seas in the northwestern Pacific Ocea…
https://en.wikipedia.org/wiki/Taiwan
+ 3 more evidence sources
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“Before the MBE, AAIW was colder and fresher”
VERIFIED
The evidence from 'Southern Ocean Intermediate Waters Held the Key to Earth's CO2 Past...' explicitly asks 'What made AAIW colder and fresher before the MBE?', confirming this state existed prior to the event.
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web search NEUTRAL — PRIOR definition: preceding in time or in order; earlier or former; previous. See examples of prior used in a sentence.
https://www.dictionary.com/browse/prior
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web search NEUTRAL — PRIOR definition: 1. existing or happening before something else, or before a particular time: 2. before a…. Learn more.
https://dictionary.cambridge.org/dictionary/english/prior
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web search NEUTRAL — Usage Note: Though prior usually modifies a noun that comes after it, as in prior approval, it sometimes modifies a noun for a unit of time which precedes it, as in five years prior.
https://www.thefreedictionary.com/prior
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“After the MBE, AAIW became warmer and saltier”
VERIFIED
Web search results explicitly state the result of the transition was 'warmer, saltier intermediate water with a diminished appetite for CO2'.
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web search NEUTRAL — The Mid-Brunhes Event is a climatic shift evident in a number of marine sediment and Antarctic ice cores. It corresponds to an increase in amplitude of glacial-interglacial cycles.
https://en.wikipedia.org/wiki/Mid-Brunhes_Event
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web search NEUTRAL — The result: warmer, saltier intermediate water with a diminished appetite for CO2.“Shifts in Antarctic Intermediate Water properties coincide with atmospheric CO2 rise across the Mid-Brunhes Event.” S…
https://www.oc.ntu.edu.tw/en/news-en/37453/
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web search NEUTRAL — Antarctic Bottom Water, formed close to the icy continent, possesses a distinctive isotopic signature compared to the deeper waters moving in from the Pacific. Schematic illustration of Southern Ocean…
https://www.aol.com/lifestyle/secrets-beneath-southern-ocean…
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“prior to the MBE, Antarctica discharged more icebergs than it does today.”
VERIFIED
The evidence explicitly states: 'Proxy evidence indicates that, prior to the MBE, Antarctica discharged more icebergs than it does today.'
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web search NEUTRAL — The Mid-Brunhes Event is a climatic shift evident in a number of marine sediment and Antarctic ice cores. It corresponds to an increase in amplitude of glacial-interglacial cycles.
https://en.wikipedia.org/wiki/Mid-Brunhes_Event
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web search NEUTRAL — The Iceberg Connection. What made AAIW colder and fresher before the MBE? The researchers point to Antarctica’s icebergs (Fig. 1c). Proxy evidence indicates that, prior to the MBE, Antarctica discharg…
https://www.oc.ntu.edu.tw/en/news-en/37453/
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web search NEUTRAL — The Mid-Brunhes Event refers to a significant climate change that occurred around 430,000 years ago.
https://www.geomar.de/en/news/article/kuehlere-warmzeiten-wi…
info
“A stronger Antarctic Circumpolar Current (ACC)—estimated to have been 130%–150% more vigorous than today—amplified this effect”
SINGLE SOURCE
While the general context of the study is verified, the specific quantitative estimate of '130%-150% more vigorous' for the ACC is not explicitly detailed in the provided snippets, though the study's existence is confirmed. It is likely part of the same paper, but not independently corroborated in the snippets.
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web search NEUTRAL — Antarctic Circumpolar Current, showing branches connecting to the larger thermohaline circulation.Published estimates of the onset of the Antarctic Circumpolar Current vary, but it is commonly conside…
https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current
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web search NEUTRAL — Around 424,000 years ago, the interglacial atmospheric CO2 levels shot up by ~35 ppm from the previous interglacial period–a shift known as the Mid-Brunhes Event (MBE). Scientists have long debated th…
https://www.oc.ntu.edu.tw/en/news-en/37453/
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web search NEUTRAL — The Antarctic Circumpolar Current (ACC) plays a central role in regulating the global ocean circulation, climate and Antarctic Ice Sheet dynamics. Yet the spatiotemporal variability of the ACC during …
https://pmc.ncbi.nlm.nih.gov/articles/PMC12893906/
help
“After the MBE, a southward shift in the Southern Westerly Winds reduced upwelling of warm Circumpolar Deep Water onto Antarctic continental shelves”
INSUFFICIENT EVIDENCE
No evidence was found in the provided search results regarding the southward shift of Southern Westerly Winds or the reduction of upwelling of Circumpolar Deep Water.
verified
“Raúl Tapia et al, Shifts in Antarctic Intermediate Water properties coincide with atmospheric CO 2 rise across the Mid-Brunhes Event, Science Advances (2026). DOI: 10.1126/sciadv.ady4567”
VERIFIED
The title, authors (Raul Tapia), journal (Science Advances), and DOI (10.1126/sciadv.ady4567) are all explicitly confirmed in the web search results.
info Disclaimer: This analysis is generated by AI and should be used as a starting point for critical thinking, not as definitive truth. Claims are verified against publicly available sources. Always consult the original article and additional sources for complete context.