Collaborative Research: The fingerprint of abrupt temperature events throughout Greenland during the last glacial period

大西洋经向翻转环流（AMOC）是全球三维海洋环流（全球海洋传送带）的重要组成部分，包括众所周知的向北流动的墨西哥湾流，它重新分配热量，从而影响气候。AMOC预计将在未来几个世纪减弱甚至崩溃，最近的几项研究表明，这种减弱已经开始。AMOC的崩溃不仅会严重影响北大西洋地区的气候，还会削弱全球很大一部分人口赖以生存的季风降雨。研究冰芯可以揭示AMOC强度的过去变化，并可以帮助科学家更好地了解这一重要海洋环流系统的稳定性和行为。格陵兰冰芯和海洋沉积物记录表明，在最后一个冰河时期（10万至2万年前），AMOC反复崩溃和重新启动，导致一系列极端气候振荡，通常被称为Dansgaard-Oeschger （D-O）循环。每次D-O事件都包括在格陵兰冰芯观测到的一次突然的（十年尺度的）变暖事件（增加8-15摄氏度），导致数千年的气候变暖，随后逐渐冷却回完全的冰川条件。拟议的研究将从格陵兰岛的两个冰芯中获取温度记录，以确定整个格陵兰岛的地理分布以及D-O事件的强度。这些记录将提供一个空间指纹。这可以作为一种法医工具来确定D-O变暖的位置以及这些事件期间格陵兰岛周围海冰边缘的迁移。这些数据将包括在使用最先进的全球气候模式的气候模拟中，以提高我们对这些神秘事件的物理性质的理解。这项研究将为两个冰芯提供可靠的时间尺度，对更广泛的冰芯群落有益。这项工作将支持一名早期职业科学家和一名研究生，并将为公立学校提供推广服务。了解驱动地球的物理过程吗？在整个Dansgaard-Oeschger （D-O）事件中，美国的气候系统一直是古气候研究中一个重要的开放性科学问题。D-O变暖的空间格局为D-O事件的起源提供了线索，特别是关键地理区域是位于拉布拉多海还是GIN（格陵兰、冰岛、挪威）海。来自这些冰芯的超高分辨率稳定同位素记录记录了与这些突变变暖事件相关的水文循环变化。气候模型显示，南部的Dye-3冰芯比以前分析的冰芯对气候突变更为敏感，从而有可能首次观测到海因里希事件（一种大型冰山从冰川上断裂并穿越北大西洋的自然现象）的温度印记，以及有史以来观测到的最大的D-O变暖。同位素气候模式模拟将通过D-O事件和heinrich事件对二级同位素参数（氘和17O过量）的变化提供更好的解释。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Atlantic Meridional Overturning Circulation (or AMOC) is an important part of the global three-dimensional ocean circulation (global ocean conveyor belt) that includes the well-known, northward-flowing Gulf Stream current that redistributes heat and thereby affects climate. The AMOC is expected to weaken or even collapse in the coming centuries, with several recent studies suggesting that this weakening has already begun. The AMOC collapse would not only severely impact climate in the North Atlantic region but would also weaken the monsoon rains that a large portion of the global population depends on for their livelihood. Studying ice cores can shed light on past changes in the strength of the AMOC and can help scientists better understand the stability and behavior of this important ocean circulation system. Greenland ice cores and ocean sediment records show that during the last Ice Age (100,000 to 20,000 years ago) the AMOC repeatedly collapsed and restarted, resulting in a series of extreme climate oscillations commonly known as Dansgaard-Oeschger (D-O) cycles. Each D-O event consists of an abrupt (decadal-scale) warming episode (increase of 8-15 degrees Centigrade) observed in Greenland ice cores, leading to a few millennia of warmer climate followed by a gradual cooling back to full glacial conditions. The proposed research will develop temperature records from two Greenland ice cores to determine both the geographic distribution as well as the intensity of the D-O events throughout Greenland. These records will provide a spatial ?fingerprint? of the D-O events, which can be used a forensic tool to determine the location of D-O warming and the migration of the sea-ice edge around Greenland during these events. These data will be included in climate simulations using state-of-the-art global climate models to improve our understanding of the physical nature of these enigmatic events. The research will contribute to reliable timescales for the two ice cores, with benefits to the wider ice core community. The work will support an early-career scientist and a graduate student and will also provide outreach to public schools. Understanding the physical processes that drive the Earth?s climate system throughout a Dansgaard-Oeschger (D-O) event remains an important open scientific question in paleoclimate research. The spatial pattern of D-O warming holds clues to the origin of D-O events, in particular whether the critical geographic area is located in the Labrador Sea or in the GIN (Greenland, Iceland, Norwegian) seas. Ultra-high-resolution stable isotope records from these ice cores document changes in the hydrological cycle associated with these abrupt warming episodes. Climate models show that the southern Dye-3 ice core is more sensitive to abrupt climate change than previously analyzed ice cores, giving the possibility of observing for the first time the temperature imprint of a Heinrich event (a natural phenomenon in which large armadas of icebergs break off from glaciers and traverse the North Atlantic Ocean), as well as the largest D-O warmings ever observed. Isotope enabled climate model simulations will provide improved interpretation of changes in second-order isotope parameters (deuterium- and 17O excess) through D-O and Heinrich-events.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.