2023-07-21 バッファロー大学(UB)
A new study that analyzes ancient soil once stored at the University at Buffalo is causing a worrisome rethinking of the history of Greenland’s ice sheet and reveals its fragile nature today.
◆そして新しい研究では、41.6万年前にはグリーンランドは緑豊かな土地だったことが判明しました。氷のない環境で流れる水によって堆積した土壌から直接的な証拠が見つかりました。
◆これは、42.4万年から37.4万年前の穏やかな温暖期に氷が大部分消失したという初めての確実な証拠です。これによりグリーンランドの過去を理解することが将来の気候変動に対する対応に重要であるとわかりました。
◆グリーンランドの氷は気候変動に非常に敏感であり、永久に融ける危険性があります。氷の溶け込みが進むと、約23フィートの海面上昇が発生し、世界中の沿岸地域が危険にさらされることになります。
＜関連情報＞
- https://www.buffalo.edu/news/releases/2023/07/ancient-soil-shows-greenland-melted-recently.html
- https://www.science.org/doi/10.1126/science.ade4248
海洋同位体ステージ11におけるグリーンランド北西部の氷河化 Deglaciation of northwestern Greenland during Marine Isotope Stage 11
Andrew J. Christ ,Tammy M. Rittenour,Paul R. Bierman,Benjamin A. Keisling,Paul C. Knutz,Tonny B. Thomsen ,Nynke Keulen ,Julie C. Fosdick ,Sidney R. Hemming,Jean-Louis Tison ,Pierre-Henri Blard ,Jørgen P. Steffensen,Marc W. Caffee,Lee B. Corbett,Dorthe Dahl-Jensen,David P. Dethier,Alan J. Hidy ,Nicolas Perdrial,Dorothy M. Peteet,Eric J. Steig, and Elizabeth K. Thomas
Science Published:20 Jul 2023
DOI:https://doi.org/10.1126/science.ade4248
Editor’s summary
Measurements made on subglacial sediment from the Camp Century ice core in northwestern Greenland show that the location was ice free during the interglacial that occurred around 400,000 years ago. Christ et al. used luminescence dating and cosmogenic nuclide data to show that the sediment was deposited under ice-free conditions after having been exposed at the surface to sunlight fewer than 16,000 years earlier. The absence of ice at that location means that the Greenland Ice Sheet must have contributed more than 1.4 meters of sea-level equivalent to the high sea-level stand, when the average global air temperature was similar to what we will soon experience because of human-caused climate warming. —H. Jesse Smith
Abstract
Past interglacial climates with smaller ice sheets offer analogs for ice sheet response to future warming and contributions to sea level rise; however, well-dated geologic records from formerly ice-free areas are rare. Here we report that subglacial sediment from the Camp Century ice core preserves direct evidence that northwestern Greenland was ice free during the Marine Isotope Stage (MIS) 11 interglacial. Luminescence dating shows that sediment just beneath the ice sheet was deposited by flowing water in an ice-free environment 416 ± 38 thousand years ago. Provenance analyses and cosmogenic nuclide data and calculations suggest the sediment was reworked from local materials and exposed at the surface <16 thousand years before deposition. Ice sheet modeling indicates that ice-free conditions at Camp Century require at least 1.4 meters of sea level equivalent contribution from the Greenland Ice Sheet.
