{"id":284071,"date":"2026-02-06T15:23:09","date_gmt":"2026-02-06T15:23:09","guid":{"rendered":"https:\/\/www.newsbeep.com\/ie\/284071\/"},"modified":"2026-02-06T15:23:09","modified_gmt":"2026-02-06T15:23:09","slug":"scientists-found-the-coldest-seawater-in-history-from-when-snowball-earth-reached-freezing-temperatures-of-minus-15-celsius","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ie\/284071\/","title":{"rendered":"Scientists Found the Coldest Seawater in History from when Snowball Earth Reached Freezing Temperatures of Minus 15\u00b0 Celsius"},"content":{"rendered":"

\"Covered <\/a>Illustration of \u201cSnow Ball\u201d Earth. <\/p>\n

Earth froze over 717 million years ago. Ice crept down from the poles to the equator, and the dark subglacial seas suffocated without sunlight to power photosynthesis. Earth became an unrecognizable, alien world\u2014a \u201csnowball Earth<\/a>,\u201d where even the water was colder than freezing.<\/p>\n

In\u00a0Nature Communications,\u00a0researchers reported<\/a>\u00a0the first measured sea temperature from a snowball Earth episode: \u221215\u00b0C\u2009\u00b1\u20097\u00b0C. If this figure holds up, it will be the coldest measured sea temperature in Earth\u2019s history.<\/p>\n

For water to be that cold without freezing, it would have to be very salty. And indeed, the team\u2019s analysis suggests that some pockets of seawater during the Sturtian snowball glaciation, which lasted 57 million years, could have been up to 4 times saltier than modern ocean water.<\/p>\n

\u201cWe\u2019re dealing with salty brines,\u201d said\u00a0Ross Mitchell<\/a>, a geologist at the Institute of Geology and Geophysics of the Chinese Academy of Sciences. \u201cThat\u2019s exactly what you see in Antarctica today,\u201d he added, except that snowball Earth\u2019s brines were a bit colder than even the \u221213\u00b0C salty slush of Antarctica\u2019s ice-covered Lake Vida today.<\/p>\n

\"\" <\/a>In Antarctic lakes such as Lake Fryxell, fresh water freezes over briny liquid water. New research suggests that the liquid seawater during \u201csnowball Earth\u201d was up to 4 times saltier than modern ocean water, meaning it could reach much lower temperatures before freezing. Credit:\u00a0Joe Mastroianni, National Science Foundation\/Wikimedia Commons<\/a><\/p>\n

Past Iron<\/p>\n

The Sturtian snowball was a runaway climate catastrophe that occurred because ice reflects more sunlight than land or water. Ice reflected sunlight, which cooled the planet, which made more ice, which reflected more sunlight and so on, until the whole world ended up buried under glaciers that could have been up to a kilometer thick.<\/p>\n

This unusual time left behind unusual rocks: Rusty red iron formations that accumulated where continental glaciers met the ice-covered seas. To take snowball Earth\u2019s temperature, the team devised a new way to use that iron as a thermometer.<\/p>\n

\"A <\/a>Scientists used information about the iron in formations like this one to estimate the temperature of Earth\u2019s ocean 717 million years ago. Credit:\u00a0James St. John\/Flickr<\/a>,\u00a0CC BY 2.0<\/a><\/p>\n

Iron formations accumulate in water that\u2019s rich in dissolved iron. Oxygen transforms the easily dissolved, greenish \u201cferric\u201d form of iron into rusty red \u201cferrous\u201d iron that stays solid. That\u2019s why almost all iron formations are ancient, relics of a time before Earth\u2019s atmosphere started filling with oxygen about 2.4 billion years ago, or from the more recent snowball Earth, when the seas were sealed under ice. Unable to soak up oxygen from the air or from photosynthesis, snowball Earth\u2019s dark, ice-covered seawater drained of oxygen.<\/p>\n

Iron-56 is the most common iron isotope, but lighter iron-54 rusts more easily. So when iron rusts in the ocean, the remaining dissolved iron is enriched in the heavier isotope. Over many cycles of limited, partial rusting\u2014like what happened on the anoxic Archean Earth\u2014this enrichment grows, which is why ancient iron formations contain isotopically very heavy iron compared to iron minerals that formed after Earth\u2019s atmosphere and oceans filled with oxygen.<\/p>\n

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Snowball Earth\u2019s iron is heavy, too, even more so than iron formations from the distant, preoxygen past. The researchers realized that temperature could be the explanation: Iron minerals that form in cold water end up istopically heavier. We don\u2019t know exactly how hot it was when the ancient iron formations accumulated, but it was likely warmer than during snowball Earth, when glaciers reached the equator. Using a previous estimate of 25\u00b0C for the temperature of Archean seawater, the team calculated that the waters that formed the snowball Earth iron formations would likely have been 40\u00b0C colder.<\/p>\n

\u201cIt\u2019s a very interesting, novel way of getting something different out of iron isotope data,\u201d said geochemist\u00a0Andy Heard<\/a>\u00a0of the Woods Hole Oceanographic Institution, who was not involved in the study. \u201cIt\u2019s a funny, backwards situation to be in where you\u2019re using even older rocks as your baseline for understanding something that formed 700 million years ago.\u201d<\/p>\n

In part because of that backward situation, Heard thinks the study is best interpreted qualitatively as strong evidence that seawater was really cold, but maybe not that it was exactly \u221215\u00b0C.<\/p>\n

The team also analyzed isotopes of strontium and barium to determine that snowball Earth\u2019s seawater was up to 4 times saltier than the modern ocean.\u00a0Jochen Brocks<\/a>\u00a0of the Australian National University, who wasn\u2019t involved in the study, said the researchers\u2019 results align with his own salinity analysis of snowball Earth sediments from Australia based on a different method. Those rocks formed in a brine that Brocks thinks was salty enough to reach \u22127\u00b0C before freezing. Another group reaching a similar conclusion using different methods makes that extreme scenario sound a lot more plausible, he said.<\/p>\n

\u201cIt was very cool to get the additional confirmation it was actually very, very cold,\u201d he said.<\/p>\n","protected":false},"excerpt":{"rendered":"Illustration of \u201cSnow Ball\u201d Earth. Earth froze over 717 million years ago. Ice crept down from the poles…\n","protected":false},"author":2,"featured_media":284072,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[464,34375,61,60,82,136854],"class_list":{"0":"post-284071","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-cold","9":"tag-ice-age","10":"tag-ie","11":"tag-ireland","12":"tag-science","13":"tag-snowball-earth"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/284071","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=284071"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/284071\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/284072"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=284071"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=284071"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=284071"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}