Lost cold Antarctic deserts inferred from unusual sulfate formation and isotope signatures
Lost cold Antarctic deserts inferred from unusual sulfate formation and isotope signatures
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从不寻常的硫酸盐形成和同位素特征推断消失的寒冷南极沙漠
DOI：
10.1038/ncomms8579
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发表时间：
2015
影响因子：
16.6
通讯作者：
Eric Tonui
中科院分区：
文献类型：
--
作者：
Tao Sun;R. Socki;David L. Bish;Ralph P. Harvey;Huiming Bao;P. Niles;Ricardo Cavicchioli;Eric Tonui
南极冰盖对全球海洋环流和气候有着重要影响。大陆冰川沉积物提供了南极内陆冰川历史的直接物理证据，但这些数据很少。在这里，我们调查了冰盖演变的一个新的指标：硫酸盐内的冰川沉积物从刘易斯悬崖冰舌的中部横贯山脉。硫酸盐具有独特的同位素特征，包括芒硝中δ 34 S高达+50‰，当代融水池中溶解硫酸盐的Δ 17 O高达+2.3‰，以及极负的δ 18 O低至−22.2‰。同位素数据表明，硫酸盐形成的环境条件类似于今天的麦克默多干谷，这表明自中新世以来，南极和跨南极山脉之间可能存在无冰的寒冷沙漠，当时冰盖的大小比今天小，但总体上与现代全球水文循环相似。由于缺乏陆地数据，过去对东南极冰盖大小的了解有限。在这里，作者提出了硫酸盐的同位素数据从刘易斯悬崖冰舌冰碛，这表明在南极洲中部的中新世以来的暂时存在的无冰条件。
The Antarctic ice cap significantly affects global ocean circulation and climate. Continental glaciogenic sedimentary deposits provide direct physical evidence of the glacial history of the Antarctic interior, but these data are sparse. Here we investigate a new indicator of ice sheet evolution: sulfates within the glaciogenic deposits from the Lewis Cliff Ice Tongue of the central Transantarctic Mountains. The sulfates exhibit unique isotope signatures, including δ34S up to +50‰ for mirabilite evaporites, Δ17O up to +2.3‰ for dissolved sulfate within contemporary melt-water ponds, and extremely negative δ18O as low as −22.2‰. The isotopic data imply that the sulfates formed under environmental conditions similar to today’s McMurdo Dry Valleys, suggesting that ice-free cold deserts may have existed between the South Pole and the Transantarctic Mountains since the Miocene during periods when the ice sheet size was smaller than today, but with an overall similar to modern global hydrological cycle. Due to a paucity of terrestrial data, knowledge of the size of the East Antarctic ice sheet in the past is limited. Here, the authors present isotope data of sulfates from the Lewis Cliff Ice Tongue moraine, which suggest temporary existence of ice-free conditions in central Antarctica since the Miocene.