He \u2014 an assistant professor of marine and environmental sciences at Northeastern \u2014 discovered something that could be a cause for a radical reinterpretation.<\/p>\n
Instead of the waters of these two oceans oscillating back and forth as temperatures rose, He and his co-researchers, using radiocarbon dating of deepwater seabed sentiments<\/a>, observed that the bottom water formations \u201cweakened simultaneously,\u201d he says.<\/p>\n Deep water storage<\/p>\n Antarctic Bottom Water \u2014 or AABW, in marine scientist speak \u2014 \u201cforms when extremely cold, salty water sinks near Antarctica due to sea ice formation,\u201d He says.<\/p>\n \u201cThis dense water then flows northward along the ocean floor, eventually rising at the surface,\u201d He continues. How much of and how quickly this deep water rises is called the overturn rate, a process that links all the oceans together in a cycle called thermohaline circulation.<\/p>\n The AABW formation sequesters massive quantities of \u201catmospheric CO2 in the deep ocean for centuries,\u201d He says. If its overturn rate increases \u2014 that is, if the carbon-trapping waters in the deep ocean rise to the surface and release that CO2 more quickly \u2014 it could represent \u201ca critical tipping point that could dramatically alter regional climates, disrupt weather patterns globally and reduce the ocean\u2019s capacity to absorb carbon dioxide.\u201d<\/p>\n Radiocarbon dating \u2026 water?<\/p>\n Carbon dating as a concept (or even just the phrase) is familiar to many \u2014 but how do we carbon date an ocean, let alone its movements?<\/p>\n He says that radiocarbon \u2014 a particular isotope of carbon, \u201cradio\u201d because it is radioactive and thus decays at a predictable rate \u2014 \u201cacts as a natural clock in seawater.\u201d\u00a0<\/p>\n When seawater is at the surface, it acquires the contemporary radiocarbon isotope. As it sinks (perhaps becoming part of the AABW formation), the radiocarbon then decays at the known rate, and eventually deposits on the seafloor, where scientists can collect their core samples.<\/p>\n But, with the aid of a \u201cstate-of-the-art Earth System Model, in which we track both water movement and radiocarbon through time,\u201d He says, they made a surprising observation: \u201cWhat looked like faster-moving deep water in the Southern Ocean 17,000 years ago was actually slower-moving water that just started with younger radiocarbon ages at the surface.\u201d<\/p>\n In the early deglaciation period, between 15,000 and 17,000 years ago, the sea ice receded and the formation of Antarctic Bottom Water weakened \u2014 that is, the process that creates the AABW slowed, capturing less CO2 over time.<\/p>\n A climatic bellwether<\/p>\n According to the researchers\u2019 model, this suggests that two bottom water formations \u2014 the North Atlantic and the Antarctic \u2014 weakened simultaneously, like two massive storage units suddenly failing to accept any more CO2.<\/p>\n \u201cSuddenly,\u201d here, is on the order of about two millennia, but accounted for half of the total CO2 rise throughout the full 8,000-year deglaciation, according to the paper.<\/p>\n \u201c\u200b\u200bWe\u2019re seeing similar patterns today,\u201d He writes. \u201cRecent observations show AABW is weakening as the Southern Ocean warms.\u201d<\/p>\n \u201cUnderstanding how these massive water masses behaved during past climate transitions helps us better predict future changes,\u201d He says.\u00a0<\/p>\n As the oceans continue to warm, deep ocean carbon trapping will slow down more and more, \u201cpotentially affecting global heat distribution, carbon sequestration and regional climate patterns.\u201d<\/p>\n Noah Lloyd is the assistant editor for research at Northeastern Global News and NGN Research. Email him at n.lloyd@northeastern.edu<\/a>. Follow him on X\/Twitter at @noahghola<\/a>.<\/p>\n![\"Chengfei](\"https:\/\/www.europesays.com\/ie\/wp-content\/uploads\/2025\/10\/Chengfei-He.jpg\")
\u201cUnderstanding how these massive water masses behaved during past climate transitions helps us better predict future changes,\u201d He says. Photo by Matthew Modoono\/Northeastern University<\/p>\n