EAPSI: Evaluating the Impact of an Unusual Meteorite at the Onset of Younger Dryas Using a Greenland Ice Core

新仙女木期是末次冰期之后距今12，900年至11，600年的一个主要降温期。这种突然冷却的原因还不清楚。一个极具争议的假说认为，一些陨石或彗星的撞击引发了冰川前阿加西湖（五大湖）的融水突然释放，扰乱了海洋环流，最终导致长期冷却。最近，在新仙女木开始时，在格陵兰冰芯中发现了非常高的铂和低的铱浓度，表明异常富含铂的铁陨石撞击。然而，另一项研究表明，这些异常浓度可能来自古代陆地物质的风化。因此，本项目将分析格陵兰岛的另一个冰芯，以证实最近的发现并确定陨石的性质。该项目将与韩国仁荷大学的Sungmin Hong博士及其韩国极地研究所的合作者合作进行，他们是冰芯铂和铱分析专家。这项研究将为新仙女木事件期间气候突然变冷的原因提供深入的见解，并促进对气候变化机制的理解。这项研究将确定北格陵兰冰芯项目（NGRIP）冰芯中新仙女木事件开始时的铂和铱浓度。这些分析在技术上具有挑战性，因为冰样品需要对NGRIP冰芯进行去污，这些冰芯可能在钻探过程中受到污染，并且需要对铂金属进行高灵敏度测量，这些金属在冰中的浓度预计极低（10- 15克/克或毫微微克/克）。该项目旨在在超净工作条件下净化NGRIP冰芯，并使用扇形场电感耦合等离子体质谱法（ICP-SFMS）测量铂和铱。这个NSF EAPSI奖是与韩国国家研究基金会合作资助的。

The Younger Dryas is a major cooling period from 12,900 to 11,600 years before present subsequent to the last glaciation. The cause of this abrupt cooling is poorly understood. A highly controversial hypothesis suggests that a number of meteorite or comet impacts triggered sudden release of meltwater from proglacial Lake Agassiz (Great Lakes), disrupting oceanic circulation, and eventually leading to long term cooling. Recently, remarkably high Platinum and low Iridium concentrations have been discovered in the Greenland ice core at the onset of Younger Dryas, indicating an unusually Platinum enriched iron meteorite impact. However, another study suggested that these abnormal concentrations could be from weathering of ancient terrestrial material. Therefore, this project will analyze another ice core from Greenland to substantiate the recent discovery and determine the nature of meteorite. The project will be performed in collaboration with Dr. Sungmin Hong at Inha University in Korea, and his collaborators at Korea Polar Research Institute, who are experts in Platinum and Iridium analyses in ice cores. This research will provide insight into the cause of an abrupt cooling climate during Younger Dryas, and advance understanding of mechanisms of climate change.The research will determine Platinum and Iridium concentrations at the onset of Younger Dryas in the North Greenland Ice Core Project (NGRIP) ice core. These analyses are technically challenging as ice samples require decontamination of the NGRIP ice core, which could have been contaminated during drilling, and high sensitivity measurements of platinum metals, whose concentrations in the ice are expected to be extremely low (in 10-15g/g or femtogram/g). This project aims to decontaminate the NGRIP ice core in ultraclean working conditions and measure Platinum and Iridium using sector-field inductively coupled plasma mass spectrometry (ICP-SFMS). This NSF EAPSI award is funded in collaboration with the National Research Foundation of Korea.