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An international team decided to test that picture across the whole western edge at once. What they got back \u2013 the age of the gas \u2013 suggested the ice had once pulled back far further than anyone assumed.<\/p>\n
Tracing the gas source<\/p>\n
The gas is methane, a more potent greenhouse driver than carbon dioxide. Researchers had already spotted it leaking from glacier fronts at scattered sites around the world.<\/p>\n
An earlier paper<\/a> confirmed methane streaming out of one Greenland outlet too. <\/p>\n But no one had checked whether this was one strange site or something happening along the entire edge of an ice sheet.<\/p>\n That\u2019s the question Jade Hatton tackled with an international team based at Charles University<\/a> in Prague. <\/p>\n Her team sampled 26 streams of meltwater flowing from the western flank of Greenland\u2019s ice.<\/p>\n Sampling the ice edge<\/p>\n The transect stretched more than 1,200 miles, from far northwest Greenland down to the southwest. <\/p>\n Each meltwater stream pouring from under the ice carried what the team wanted: dissolved subglacial methane<\/a>, plus chemical fingerprints of where it came from.<\/p>\n Field crews drilled more than 3,900 feet through the ice to reach the bed, pulling up sediment cores and water samples. <\/p>\n Down there, oxygen runs out fast. Whatever microbes live in that dark slurry have to do without it.<\/p>\n An ancient signature<\/p>\n Back in the lab, the team ran two main tests. First, they read the chemical signature of the gas to determine whether it came from microbes or from deep geological sources. <\/p>\n Then, they used radiocarbon dating to nail down its age. The isotopes pointed straight to microbes. <\/p>\n Methane made by anaerobic microbes chewing through decaying plant material in oxygen-starved sediments \u2013 not gas seeping up from deep rock formations.<\/p>\n The radiocarbon results were the surprise. Those samples came back at 1,500 to 4,400 years old. <\/p>\n That age tells a backward story. The radiocarbon clock implies microbes have been producing the gas from buried organic matter under the ice. <\/p>\n For that to have happened, vegetation must once have grown on land now covered.<\/p>\n What the evidence suggests<\/p>\n The math points to a known warm stretch in Earth\u2019s recent past. Scientists call it the Holocene Thermal Maximum \u2013 roughly 11,000 to 5,000 years ago, when the Arctic ran warmer than usual, broadly comparable to today\u2019s.<\/p>\n Greenland\u2019s ice sheet had to have been smaller during that warm period for plants to take hold. Smaller, even, than it is right now.<\/p>\n The evidence suggests boreal forest and tundra crept onto that exposed land. Plants took root, died, and left carbon-rich material in the sediment year after year.<\/p>\n Then, the climate cooled again. Ice readvanced and overrode that exposed land. <\/p>\n Plant remains got sealed under thousands of feet of frozen weight. Down in the dark, microbes kept eating away at the buried carbon, century after century.<\/p>\n A self-feeding loop<\/p>\n Modern glacial retreat<\/a> is replaying that earlier turn. As the ice margin pulls back today, meltwater finds new paths through the bed and flushes out the methane those long-buried microbes have been making.<\/p>\n Western Greenland\u2019s land-based glaciers now release roughly 790 tons of dissolved methane each year. That buried organic matter could sustain the flow for another 200 years at least.<\/p>\n A feedback is in the making. As Greenland melts, more pathways open beneath the ice. Methane escapes. That gas carries its own warming effect \u2013 one that could push the melt even further.<\/p>\n Antarctica looms larger<\/p>\n The same setup likely exists at the other pole, on a much bigger scale. <\/p>\n An older study<\/a> flagged the possibility of vast methane reservoirs sitting beneath Antarctica, where buried organic matter is far greater than anything Greenland holds.<\/p>\n If Antarctic ice continues thinning and its bed becomes more connected by meltwater, the same kind of slow methane transport could amplify, dwarfing Greenland\u2019s contribution.<\/p>\n The survey covered western Greenland\u2019s margin, leaving eastern and northern sectors uncharted \u2013 meaning total flux could be higher than estimated. <\/p>\n The 200-year projection also rests on a degradation model, not direct measurement, and carries a wide uncertainty range.<\/p>\n The ultimate irony<\/p>\n Until this work, no one had measured methane across the full edge of an ice sheet. <\/p>\n The age of the gas pins it to a specific past climate, dating Greenland\u2019s last big retreat with new precision.<\/p>\n Existing ice sheet models don\u2019t yet capture this dynamism. A separate study<\/a> estimates Greenland is locked into roughly a foot of sea-level rise<\/a> from melt already committed.<\/p>\n The methane evidence says that floor is too low. Greenland\u2019s ice has shown it can swing farther than the models forecast \u2013 and as it pulls back, it feeds the warming that drives more retreat.<\/p>\n \u201cThe ultimate irony is that as it retreats, the ice sheet itself further contributes to those methane emissions,\u201d said Alun Hubbard, a professor at the University of Oulu<\/a> and co-author of the study.<\/p>\n The study is published in the journal Nature Geoscience<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"For years, scientists sampling meltwater streams at Greenland\u2019s glacier margins found methane dissolved in the water. This methane…\n","protected":false},"author":2,"featured_media":661067,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[49,48,66],"class_list":["post-661066","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ca","tag-canada","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/661066","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=661066"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/661066\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/661067"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=661066"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=661066"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=661066"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}