Collaborative Research: REU: Calibrating the Water Isotope Thermometer in Antarctica Using Abrupt Heinrich Event Signatures in the EDML Ice Core

这个项目试图回答这个问题，“在最后一个冰河时期，南极洲有多冷？”这一信息将有助于预测未来由于人类排放吸热气体而导致南极洲变暖的幅度，并对未来50至100年南极冰盖和海平面的稳定性产生影响。提出的方法使用了一种新的“气体温度计”，该温度计基于被困在雪中的空气，并以气泡的形式保存在冰中，可以从冰芯中回收。新的温度计使用了来自冰中的气泡的氮和氩同位素的比例（给定元素的同位素具有不同数量的中子），并在过去20年里成功地在格陵兰岛使用，表明格陵兰岛在最后一个冰河时期的温度比现在低约35华氏度。南极洲的研究比格陵兰岛更具挑战性，但最近气体温度计的改进使得研究南极洲的温度历史并了解其在人类影响下的未来变得可行。本项目将对研究生和本科生进行这些方法的培训。获得极地冰盖过去温度的经典方法使用水的同位素（18O和2H），并已被证明存在偏差，例如，将末次盛冰期格陵兰岛的冷却程度低估了2倍。该项目旨在使用最近改进的基于N2和Ar同位素的惰性气体温度计校准东南极洲的水同位素温度计。该项目将与欧洲同事合作，使用来自东南极洲（Dronning Maud Land）岩心的冰。此外，来自南极西部冰芯的相同年龄的冰样本将作为基准进行测量。该项目还将沿着南极东部冰芯的长度对甲烷和N2同位素进行有针对性的测量，以更好地了解冰芯的气候历史和冰川演化。这些测量将使水同位素温度计能够根据观测到的南极东部岩心的气体年龄-冰期差异进行第二次独立校准。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。

This project seeks to answer the question, "How cold was Antarctica during the last ice age?" This information will help to predict the magnitude of future warming in Antarctica due to human emissions of heat-trapping gases, with implications for the stability of Antarctic ice sheets and sea level in the next 50 to 100 years. The proposed method uses a new "gas thermometer" based on air trapped in snow and preserved as air bubbles in ice that can be recovered from ice cores. The new thermometer uses ratios of nitrogen and argon isotopes (an isotope of a given element has a different number of neutrons) from the air bubbles in the ice and has been used successfully in Greenland over the past two decades to show that Greenland temperatures during the last ice age were ~35 degrees Fahrenheit colder than at present. Antarctica is more challenging to study than Greenland, but recent improvements in the gas thermometer now make it practical to address Antarctica's temperature history and inform its future under human influence. This project will train graduate and undergraduate students in these methods.The classical method for obtaining past temperatures on polar ice sheets uses the isotopes of water (18O and 2H) and has been shown to suffer from biases, for example underestimating Greenland cooling in the Last Glacial Maximum by a factor of 2. This project seeks to calibrate the water-isotope thermometer in East Antarctica using the recently improved inert-gas thermometer based on isotopes of N2 and Ar. The project will use ice from a core from East Antarctica (Dronning Maud Land) in collaboration with European colleagues. Further, ice samples of the same age from a West Antarctic ice core will be measured as a benchmark. The project will also perform targeted measurements of methane and N2 isotopes along the length of the East Antarctic ice core, to better understand the climate history and firn evolution of the core. These measurements will enable a second, independent calibration of the water-isotope thermometer from the observed gas-age – ice-age difference along the East Antarctic core.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.