Paul Bierman: LL 13.03.2025 скачать в хорошем качестве

Paul Bierman: LL 13.03.2025

A landscape under the ice: Camp Century, Greenland In northwest Greenland, frozen beneath more than 1300 meters of ice, lies a frozen landscape. In 1966, US Army drillers working at Camp Century, the nuclear-powered base inside the ice sheet, completed the world’s first deep ice core. They kept drilling and recovered 3.44 meters of frozen sub-glacial material––ice and sediment. This archive was stored frozen in the US and Denmark for almost 60 years and little studied. Since 2019, an international team, supported in part by the US NSF, has been analyzing this material. Based on research I did for my 2024 book, When the Ice is Gone, I will explain how and why the US Army came to drill a nearly mile-long ice core in Greenland. I will then synthesize a variety of new data to describe processes that formed and transformed this under-ice landscape. CT scans and physical properties of the sediment show a landscape shaped by ice (till) and then by gravity flows and moving water (bedded sand). Geochronology tells us the till was deposited at some time between 1.4 and 3.2 Mya; geochemical analysis of porewater and SEM microanalysis of grain coatings indicate that the till was deeply weathered, but in situ 10-Be demands that the surface was eroded and that weathering extended meters below it. When the ice melted ~400 kya (MIS 11 super interglacial), the permafrost softened, and the till slumped. It was reworked by flowing water before ice once again covered the site. Thousands of preserved plant macrofossils, found throughout the core and representing several dozen taxa, reveal that tundra vegetation covered the site during both interglacial periods represented in the core material. The plant species present indicate a mosaic of ecological niches the result of geomorphic heterogeneity – low spots with standing water, xeric outcrops and bare soil, frequent disturbance, and soils with different pH. Our work shows the potential for sub-ice cores to reveal the history of Arctic landscapes now covered in ice. That information will become increasingly relevant as global warming rapidly changes the Earth’s glaciated regions. Paul Bierman's website: https://www.paulbierman.net/ On Bluesky: https://bsky.app/profile/paul-bierman...