Initiation of Fennoscandian ice-sheet retreat during the last deglaciation
Initiation of Fennoscandian ice-sheet retreat during the last deglaciation
复制标题
末次冰消期期间芬诺斯坎迪亚冰盖开始退缩
作者：
S. Lehman;G. Jones;L. Keigwin;E. Andersen;G. Butenkoi;S. Østmo
尽管劳伦蒂冰盖南缘在最后一次冰川消融期间的退缩历史已经众所周知了几十年1-3，最近得到了加速器质谱仪(AMS)对墨西哥湾融水和北大西洋亚热带回旋5的放射性碳测年证据的支持，但13年前芬诺斯坎迪亚冰盖的退缩历史仍然很少有文献记载。根据挪威海峡(北海)一系列快速沉积的超耕沉积物的AMS 14C测年和同位素分析，我们发现芬诺斯坎迪亚冰盖南缘退缩了15KYR BP(现在之前)，比以前推测的时间早了大约2000年。航道沉积物中的氧同位素分析证实了来自挪威深海沉积物岩心的早期证据，即由于从∼15-14.5KYR BP开始的冰盖排放，盐度较低。6)。最近对14C时间刻度的重新校准表明，挪威海内冰川消融的开始发生在夏季日照迅速增加的时间段，从∼18000年开始。7)，这表明冰盖退缩可能是由于日照增加作用于对气候特别敏感的冰盖构造造成的。此时排入挪威海的淡水和冰山到达了北大西洋，可能导致了短暂的极端海洋冷却和北大西洋深水产量的减少。这些因素也可能帮助短暂地扭转了北美已经在进行的冰川消融趋势(Erie Interstade)。
ALTHOUGH the retreat history of the southern margin of the Laurentide ice sheet during the last deglaciation has been well known for several decades1–3 and recently supported by evidence from accelerator mass spectrometer (AMS) radiocarbon dating of meltwater in the Gulf of Mexico4 and the North Atlantic subtropical gyre5, the retreat history of the Fennoscandian ice sheet before 13kyr ago is still poorly documented. From AMS 14C dating and isotopic analysis of a rapidly deposited series of supra-till sediments in the Norwegian Channel (North Sea), we find that the southern margin of the Fennoscandian ice sheet was in retreat by 15 kyr BP (before present), approximately 2,000 yr earlier than previously supposed. Oxygen isotope analyses in the channel sediments confirm earlier evidence from deep Norwegian Sea sediment cores for low salinity due to ice sheet discharge beginning ∼15–14.5 kyr BP (ref. 6). Recent recalibration of the 14C timescale indicates that the onset of deglaciation within the Norwegian Sea occurred during an interval of rapidly increasing summer insolation beginning∼18,000 calendar yr BP (ref. 7), suggesting that ice-sheet retreat may have been caused by increasing insolation acting on a particularly climate-sensitive ice-sheet configuration. Fresh water and icebergs discharged into the Norwegian Sea at this time reached the North Atlantic and may have contributed to a brief interval of extreme oceanic cooling8 and reduced production of North Atlantic Deep Water9,10. These factors may also have helped to briefly reverse the deglaciation trend (Erie Interstade) already underway in North America.