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

大西洋子午线翻转环流(或称AMOC)是全球三维海洋环流(全球海洋传送带)的重要组成部分，其中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。预计AMOC将在未来几个世纪削弱甚至崩溃，最近的几项研究表明，这种削弱已经开始。AMOC的崩溃不仅将严重影响北大西洋地区的气候，还将削弱全球很大一部分人口赖以生存的季风雨。研究冰芯可以揭示AMOC强度过去的变化，并有助于科学家更好地了解这一重要海洋循环系统的稳定性和行为。格陵兰冰芯和海洋沉积物记录表明，在上一个冰河时代(10万至20000年前)，AMOC反复坍塌和重新启动，导致了一系列通常被称为丹斯加德-奥施格(D-O)循环的极端气候振荡。每一次D-O事件都包括在格陵兰冰芯观察到的突然(十年尺度)变暖事件(升高8-15摄氏度)，导致几千年来气候变暖，然后逐渐冷却到完全冰川条件。这项拟议的研究将开发两个格陵兰冰芯的温度记录，以确定整个格陵兰D-O事件的地理分布和强度。这些记录将提供空间指纹？这可以作为一种法医工具来确定D-O变暖的位置和这些事件期间格陵兰周围海冰边缘的迁移。这些数据将被包括在使用最先进的全球气候模型的气候模拟中，以提高我们对这些神秘事件的物理性质的理解。这项研究将有助于为两个冰芯提供可靠的时间表，使更广泛的冰芯社区受益。这项工作将支持一名职业生涯早期的科学家和一名研究生，还将向公立学校提供外联服务。在整个丹斯加德-厄施格(D-O)事件中，理解驱动地球的物理过程？S气候系统仍然是古气候研究中一个重要的开放科学问题。D-O变暖的空间模式为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位于格陵兰海(格陵兰、冰岛、挪威)。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然变暖事件相关的水文循环的变化。气候模型显示，南部的Dye-3冰芯对突然的气候变化比之前分析的冰芯更敏感，这使得首次有可能观测到海因里希事件(一种自然现象，即大量冰山从冰川中分离并横穿北大西洋)的温度印记，以及有史以来观察到的最大的D-O变暖。启用同位素的气候模型模拟将通过D-O事件和海因里希事件对二阶同位素参数(氚和17O过剩)的变化提供更好的解释。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.