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July 7, 2025—Concerning new findings about Greenland's ice sheet have scientists worried. Plus, the science of flash floods and the first human genome from ancient Egypt. —Andrea Gawrylewski, Chief Newsletter Editor | | The bank of the Guadalupe River in Center Point, Tex., on July 5, 2025. Jim Vondruska/Getty Images | | Drone's-eye view of scientists using a hand drill to pull rock cores out of an outcropping on the Greenland ice sheet in May 2024. All photos: Jeffery DelViscio/Scientific American | | Last year, Scientific American chief multimedia editor Jeffery DelViscio spent a month on the Greenland ice sheet, reporting on the work of scientists taking ice and rock cores from the Northeast Greenland Ice Stream (NEGIS) and the bedrock underneath. This massive flow of ice drains ice into the ocean, and its melt has been speeding up in the past decade. Bedrock samples under ice from an area in northwest Greenland indicate it was ice-free as recently as about 7,000 years ago when global temperatures were only a few degrees warmer than they are now. How they do it: For the project, called GreenDrill, the team uses drills perched over the ice (just below) that eat through ice and rock to extract thin "core samples" of the bedrock beneath the ice.  They note the length and features of the bedrock sample and break it apart for transport and analysis back in laboratories in the U.S. Measurements from the cores will feed into the mathematical models that attempt to simulate, and predict, what will happen to the Greenland ice–and how fast it might melt in a warming world. Over the decades, cores from ice, ocean sediment, trees, coral and other rocks and materials have given scientists an indirect way to track the timing of large and abrupt shifts in climate as far back as 123,000 years ago in the case of Greenland and 1.2 million years ago for ice extracted from Antarctica. | | Jen Christiansen; Source: Jason Briner/University at Buffalo (scientist reviewer) | | One way that scientists determine the last time bedrock under the ice was exposed to sunlight is by measuring relative amounts of different isotopes in the rock. Cosmic rays interact with minerals within the rocks, creating new isotopes (1), leaving high levels of several different kinds of isotopes (2). A glacier advancing over the bedrock seals in the isotopes (3), which continue to decay over millions of years (4). | | Why this matters: Nearly every Greenlandic glacier has thinned or retreated in the past few decades. Some have been losing mass every year for the past 27 years. If the entire Greenland ice sheet melted, global sea levels would rise by about 24 feet, inundating coastal cities, farmland and homes. "I have, for the first time ever in my career, datasets that take my sleep away at night," says Joerg Schaefer, GreenDrill's co-principal investigator. "They are so direct and tell me this ice sheet is in so much trouble." What the experts say: "Those bed materials, whether it's sediment or hard bedrock contained within it, are the words, the stories of the history of the ice sheet—it's a book of information down there that we want to read," says Jason Briner of the University at Buffalo, the other co-principal investigator of GreenDrill. | | A GreenDrill researcher breaks a bedrock core into pieces for packaging and shipment. This core was the last one the team collected before being extracted from the GreenDrill camp. Jeffery DelViscio | | | | |
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- Here's the first question of the latest science quiz, which published on Friday.
| | - If scientists had had the capability and technology, how long ago could they have recorded changes to Earth's climate? Even the relatively small human-caused warming of the troposphere (and the associated cooling of the stratosphere) could have been identified in 1885, write a group of Earth, atmospheric and climate scientists. "Based on the history of other global environmental problems," they conjecture, "it's certainly conceivable that early knowledge of the reality and seriousness of climate change could have spurred earlier global action to reduce greenhouse gas emissions." | 5 min read
| | As Jeff details in his story, the first night in his tent on the ice at the drilling site on the northeastern side of Greenland was brutal—it was -20 degrees F, the sun never set, and he awoke after limited sleep wondering if he had made a huge mistake in coming. Scientists and journalists go to the ends of the Earth to get answers.  Jeff takes a selfie on the frigid Greenland ice sheet. | | Welcome to a new week of scientific discovery. Let us know what you think of this newsletter by emailing: newsletters@sciam.com. See you tomorrow. —Andrea Gawrylewski, Chief Newsletter Editor
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