新西兰维多利亚大学Verret, Marjolaine的团队认为，永久冻土中 meteoric beryllium-10(10Bem)能指示南极东部晚中新世超干旱的开始。该项研究成果发表在2023年5月29日出版的《自然—地球科学》上。
研究人员通过评估位于麦克默多干河谷的三个站点(海拔1200-1800米)的中新世中期和第四纪晚期土壤中的 10Bem 剖面，限制了极地干旱的开始——这可能是区域冰盖稳定所必需的。研究人员将这些剖面解释为水渗透的指标，研究发现10Bem在晚中新世进入中新世中期的土壤。基于古活动层厚度和已知的 10Bem 迁移阈值的重建表明，晚中新世夏季温度为7-10°C，年降水量大于10 mm。因此，自晚中新世(约 6 Ma)以来，高海拔地区可能一直处于极度干旱的极地气候下，而不是如一些先前重建所表明的中新世中期(13.8-12.5 Ma)那样。
总之，研究结果强调，麦克默多干河谷的高海拔地区可能经历了大约14.0 ~ 6.0 Ma的温暖和潮湿的气候间隔，这与罗斯湾沿海温暖和冰减少的观测结果相一致。这一发现也表明麦克默多干河谷可能比预期的更容易受到气候变化的影响。
据了解，自从大约3390万年前(Ma)始新世-渐新世界线附近的全球变冷间隔以来，大陆规模的冰盖一直覆盖在南极洲。然而，导致现代南极洲东部持续冰盖的出现的一系列事件仍有争议。南极东部高海拔地区向永久极地干旱的转变，对于我们理解南极冰川系统对低海拔地区，地表温度变化的阈值的反应至关重要。
附：英文原文
Title: Late Miocene onset of hyper-aridity in East Antarctica indicated by meteoric beryllium-10 in permafrost
Author: Verret, Marjolaine, Trinh-Le, Cassandra, Dickinson, Warren, Norton, Kevin, Lacelle, Denis, Christl, Marcus, Levy, Richard, Naish, Tim
Issue&Volume: 2023-05-29
Abstract: Continental-scale ice sheets have covered Antarctica since an interval of global cooling near the Eocene–Oligocene boundary around 33.9 million years ago (Ma). However, the sequence of events that led to the emergence of the persistent ice sheet in modern East Antarctica remains disputed. The transition to permanent polar aridity in high elevations of East Antarctica is critical to our understanding of the threshold response of glacial systems in Antarctica to changes in surface temperature at lower elevations. Here we constrain the onset of the polar aridity—which was probably necessary for regional ice-sheet stability—by assessing meteoric beryllium-10 profiles in mid-Miocene and late Quaternary soils at three sites situated 1,200–1,800 metres above sea level in the McMurdo Dry Valleys. Interpreting these profiles as indicators of water infiltration, we find that meteoric beryllium-10 entered mid-Miocene soils as late as the late Miocene. Reconstructions based on palaeo-active-layer thickness and known thresholds of meteoric beryllium-10 mobility suggest late Miocene summer temperatures of 7–10°C with annual precipitation >10mm. Therefore, the high elevations have probably been under a hyper-arid polar climate since the late Miocene (~6 Ma) and not the middle Miocene (13.8–12.5Ma) as indicated by some previous reconstructions. Together, our findings indicate that high elevations of the McMurdo Dry Valleys probably experienced warm and wet climatic intervals from ~14.0 to 6.0Ma, which reconciles observations of coastal warmth and reduced ice in the Ross Embayment. This finding also suggests that the McMurdo Dry Valleys may be more susceptible to climate change than anticipated.
DOI: 10.1038/s41561-023-01193-4
Source: https://www.nature.com/articles/s41561-023-01193-4