{"id":568009,"date":"2026-08-13T17:40:16","date_gmt":"2026-08-13T17:40:16","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/568009\/"},"modified":"2026-08-13T17:40:16","modified_gmt":"2026-08-13T17:40:16","slug":"sediments-off-brazils-northeast-coast-reveal-sudden-changes-in-heat-transport-in-the-atlantic","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/568009\/","title":{"rendered":"Sediments off Brazil\u2019s Northeast coast reveal sudden changes in heat transport in the Atlantic"},"content":{"rendered":"

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\"Sediments<\/p>\n

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image:\u00a0<\/p>\n

Foraminifera shells viewed under a microscope. Age differences between benthic (left) and planktonic (right) specimens reveal changes in the AMOC\u00a0<\/p>\n

view more\u00a0<\/a><\/p>\n

Credit: Cristiano Chiessi<\/p>\n

According to a new study led by researchers from Brazil and Germany, the main system that transports heat from one end of the Atlantic Ocean to the other may undergo sudden changes in intensity driven by climate changes similar to those we are experiencing now, even when it is already weakened. The Atlantic Meridional Overturning Circulation (AMOC) is a vast system of ocean currents that functions as a conveyor belt for heat across the Atlantic. It carries warm water from equatorial and tropical regions to high latitudes in the North Atlantic. This helps regulate the climate in both hemispheres by moderating temperatures in Europe and parts of North America. It also influences rainfall patterns in intertropical regions of Africa and South America.<\/p>\n

Global warming has gradually weakened the AMOC, and researchers have warned for decades about the risk of the circulation reaching a critical threshold that would trigger an abrupt slowdown and radically alter the climate in various regions of the planet. Previous research indicated that the circulation could remain in this weakened, relatively stable state for thousands of years. However, a new study shows that the AMOC may be much more dynamic than previously thought, indicating that society needs to prepare not only for abrupt climate change but also for a series of such changes.<\/p>\n

The study, led by\u00a0Cristiano Mazur Chiessi<\/a>\u00a0of the School of Arts, Sciences, and Humanities at the University of S\u00e3o Paulo (EACH-USP) in Brazil and Stefan Mulitza of the University of Bremen in Germany, found evidence of two episodes of significant AMOC intensification between 17,800 and 14,800 years ago.<\/p>\n

During this period, known as \u201cHeinrich Stadial 1,\u201d the circulation was, for the most part, much weaker than it is today. However, the analysis of marine sediments by the German-Brazilian team concluded that the AMOC experienced two abrupt surges in intensity during this time: one lasting from 16,500 to 15,800 years ago and a shorter one lasting about 100 years around 15,400 years ago. During the latter episode, the AMOC\u2019s intensity even exceeded its current level.<\/p>\n

These results were\u00a0published<\/a>\u00a0in May in the journal\u00a0Nature Communications.<\/p>\n

\u201cThis is the first time it\u2019s been shown that the AMOC can experience bursts of strengthening during periods when it\u2019s weakened,\u201d says Chiessi, a specialist in paleoceanography and paleoclimatology (sciences that study the past of the ocean and climate). \u201cAs one of the article\u2019s reviewers wrote, this completely changes the way we understand the Atlantic Meridional Overturning Circulation.\u201d<\/p>\n

The main driver of the AMOC is the sinking of cold, salty water off the coast of Greenland. This deep water then flows southward and returns to the surface primarily in the Antarctic Circumpolar Current, where strong winds promote upwelling. Surface currents then carry some of this water back north, completing the circuit.<\/p>\n

However, global warming caused by greenhouse gas emissions is currently weakening this circulation. The melting of Greenland\u2019s glaciers, the warming of the Arctic Ocean, and increased rainfall in the region are reducing the salinity and density of surface waters, making it harder for them to sink.<\/p>\n

Researchers predict that this process could lead to a sudden, significant weakening of the AMOC but still do not know when or how intensely this might occur. Until recently, even the best climate models evaluated by the United Nations\u2019 Intergovernmental Panel on Climate Change (IPCC) could not predict the AMOC\u2019s evolution with sufficient accuracy. In April of this year, however, a team of researchers from the University of Bordeaux in France published improved predictions in the journal\u00a0Science Advances<\/a>, based on new observational data. According to the researchers, the AMOC could weaken by between 43% and 59% by 2100, even if all countries meet their commitments to reduce greenhouse gas emissions.<\/p>\n

A weakening of the AMOC on this scale has not occurred since the end of the last Ice Age. During the Last Glacial Maximum, the coldest period of the last Ice Age, much of Eurasia and North America was covered by gigantic glaciers over 3,000 meters high. These glaciers extended as far south as Chicago in the United States. The enormous volume of water locked in ice caused sea levels to drop 120 meters below current levels. Even during that period, the AMOC was as strong as it is today.<\/p>\n

However, a long period of deglaciation began when climate changes triggered by natural variations in the Earth\u2019s orbit raised global temperatures. After about 1,000 years of glacial melting, the AMOC experienced an abrupt decline in intensity from which it did not recover until 3,000 years later, at the end of the Heinrich Stadial 1 (HS1) event.<\/p>\n

Chiessi points out that the AMOC\u2019s previous 1,000-year weakening period does not guarantee the same timeframe for a future decline. \u201cClimate conditions were entirely different,\u201d he explains. \u201cDuring that period, the concentration of carbon dioxide in the atmosphere was lower than in the pre-industrial era. We can learn from past events, but they aren\u2019t perfect analogues.\u201d<\/p>\n

Reconstructing the past<\/p>\n

The study analyzed a marine sediment core collected in the equatorial Atlantic Ocean at a depth of 1,367 meters and approximately 189 kilometers off the coast of Maranh\u00e3o state, Northeast Brazil, during a 2012 cruise by the German research vessel\u00a0RV Maria S. Merian. During the HS1 event, as well as during other periods of weakened AMOC, precipitation increased significantly in northeastern Brazil, while it decreased dramatically in the northern Amazon and other regions farther north. \u201cThe sedimentation rate where we collected the sample was high because it rained heavily, causing significant erosion and deposition,\u201d Chiessi explains. \u201cThat allowed us to conduct many analyses. It\u2019s like having a movie with many frames per second in extremely high resolution.\u201d<\/p>\n

To estimate the strength of past ocean currents, Chiessi and Mulitza\u2019s team used a sophisticated, costly, but highly accurate method called radiocarbon ventilation dating. This technique calculates how long deep ocean water has been isolated from the atmosphere, enabling researchers to measure the speed of the currents.<\/p>\n

In each sediment layer, the researchers identified and dated shells from two types of microorganisms, both of which are called foraminifera, using carbon-14 (radiocarbon). Since this isotope is produced in the atmosphere and absorbed by microalgae only at the ocean\u2019s surface, the apparent \u201cage\u201d of these shells reflects the depth at which they formed.<\/p>\n

The shells of planktonic foraminifera (which live on the surface) are younger than those of benthic foraminifera (which live on the ocean floor). This age difference occurs because carbon-14 only reaches the depths when carried by surface waters that sink in the Greenland region.<\/p>\n

Currently, it takes 350 years for this water to circulate in the equatorial Atlantic, which is known as the \u201cventilation age\u201d of the AMOC. Therefore, as Chiessi concludes, \u201cThe age difference between a shell formed at the surface and one formed at the bottom is a direct indicator of how intense the AMOC is.\u201d<\/p>\n

Researchers Partha Sarathi Jena and Ines Beese conducted the analyses during their postdoctoral fellowships at EACH-USP and the University of Bremen, respectively. Their findings concluded that just before the HS1 event, the apparent age difference between planktonic and benthic foraminifera was 325 years. During most of the event, this difference increased to 960 years due to the weakening of the AMOC. However, during the first episode of intensification, it decreased to 450 years, and during the second, it decreased further, to 200 years.<\/p>\n

The team compared their results with those of other paleoclimatic studies, particularly estimates of precipitation during HS1 obtained by analyzing stalagmites collected at Jaragu\u00e1 Cave in Bonito in the state of Mato Grosso do Sul and at Gruta da Paix\u00e3o in Andara\u00ed in the state of Bahia. The two peaks in AMOC intensification coincide with two periods when heavy rainfall gave way to a drier climate on the continent, reducing the volume of freshwater reaching the ocean.<\/p>\n

These peaks also coincide with increases in atmospheric carbon dioxide concentrations, as recorded by studies of air bubbles trapped in Antarctic ice during HS1. Chiessi and his colleagues suggest that the two AMOC intensifications may have transported deep, carbon dioxide-rich waters \u2013 which had been relatively stagnant in the Atlantic when the AMOC was weak \u2013 into the Antarctic Circumpolar Current. Once there, the carbon dioxide was released into the atmosphere.<\/p>\n

Chiessi hopes his work will improve AMOC forecasts and help develop systems that identify climate signals anticipating abrupt changes. This would enable society to take early adaptation measures. \u201cWe\u2019ll need a great deal of resilience, but we can still prevent the worst from happening if we take action to drastically reduce greenhouse gas emissions,\u201d he notes.<\/p>\n

The study was conducted under the auspices of the\u00a0Climate Crisis and Disasters Resilience Research Center<\/a>\u00a0(CLIMARES<\/a>), a FAPESP Research, Innovation, and Dissemination Center (RIDC<\/a>). It also received support through three other projects funded by the Foundation (18\/15123-4<\/a>,\u00a023\/00355-5<\/a>, and\u00a025\/05117-0<\/a>).<\/p>\n

About S\u00e3o Paulo Research Foundation (FAPESP)
The S\u00e3o Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of S\u00e3o Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br\/en and visit FAPESP news agency at www.agencia.fapesp.br\/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http:\/\/agencia.fapesp.br\/subscribe<\/p>\n

Journal<\/p>\n

Nature Communications<\/p>\n

Article Title<\/p>\n

Centennial-scale intensifications of the Atlantic Meridional Overturning Circulation during Heinrich Stadial 1<\/p>\n

Article Publication Date<\/p>\n

19-May-2026<\/p>\n","protected":false},"excerpt":{"rendered":"image:\u00a0 Foraminifera shells viewed under a microscope. Age differences between benthic (left) and planktonic (right) specimens reveal changes…\n","protected":false},"author":2,"featured_media":568010,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[111,139,69,147],"class_list":["post-568009","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-new-zealand","tag-newzealand","tag-nz","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/568009","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=568009"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/568009\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/568010"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=568009"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=568009"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=568009"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}