Looking for Evidence of Stratospheric Ozone Depletion in Ice at South Pole

平流层中丰富的臭氧是控制地表紫外线辐射的主要因素，而紫外线辐射对地球上的生命有着重要的影响。 平流层臭氧还通过改变大气环流模式影响地球气候系统，从而影响海洋碳循环和海冰范围。 有人提出，在距今18，000年前的末次冰期结束时，平流层臭氧消耗持续了200多年，这是由一系列大规模火山爆发造成的。塔卡河火山位于南极洲西部。 这种臭氧消耗可能通过改变大气环流模式、减少南极海冰范围和增加南大洋的碳排放，加速了末次冰期最大期的结束。 该项目将测试一种新的方法，通过测量南极浅层冰样中硝酸盐的氮同位素来确定过去的地表紫外线辐射水平。 这项研究利用南极洲上空的现代臭氧洞来测试和校准过去南极臭氧洞的潜在代理或替代品。雪中硝酸盐的氮同位素组成对紫外光诱导的硝酸盐光解离的程度非常敏感。 这一特点使得测量冰芯中的氮同位素成为平流层中臭氧丰度的潜在代用品（或替代品），而平流层是地球表面紫外线辐射水平的最大决定因素。 过去地表紫外线辐射水平的代用指标将提供一种手段来检验这样一种假设，即南极洲西部一系列平流层规模的火山爆发造成的200年臭氧空洞可能在18 kyr前引发了南极洲的快速冰川消融。 我们建议测试使用硝酸盐的氮同位素作为过去的表面紫外线辐射水平的代理，通过测量硝酸盐的氮同位素在高分辨率的顶部10米以前钻浅冰芯从南极。这些冰所包含的时期是1950-2004年的共同时代（C.E.），这将使研究人员能够检查和校准众所周知的现代臭氧洞下的硝酸盐同位素富集。这将为未来两年在南极冰芯钻取的新冰芯中对18 kyr前火山活动时期的样本进行类似测量提供信息。作为该项目的一部分，南极没有实地工作。

The abundance of ozone in the stratosphere is the dominant control on surface ultra-violet radiation, which has important implications for life on Earth. Stratospheric ozone also impacts the Earth's climate system by altering atmospheric circulation patterns, with implications for the ocean carbon cycle and sea ice extent. It has been proposed that the end of the last glacial period, 18,000 years before present, was associated with a period of depleted stratospheric ozone that lasted over 200 years and was caused by a series of large eruptions from the Mt. Takahe volcano in West Antarctica. This ozone depletion may have hastened the end of the last glacial maximum by changing atmospheric circulation patterns, reducing Antarctic sea ice extent and creating increased carbon emissions from the Southern Ocean. This project will test a new method of determining past surface ultra-violet radiation levels by measuring the nitrogen isotopes of nitrate in shallow South Pole ice samples. This research utilizes the modern-day ozone hole over Antarctica to test and calibrate this potential proxy, or substitute, for past Antarctic ozone holes. The nitrogen isotopic composition of nitrate in snow is highly sensitive to the degree of ultraviolet-induced photo-dissociation of that nitrate. This feature makes the measurement of nitrogen isotopes in ice cores a potential proxy (or substitute) for the ozone abundance in the stratosphere, which is the largest determinant of ultraviolet radiation levels at the Earth's surface. A proxy for past surface ultraviolet radiation levels would provide a means to test the hypothesis that a 200-year ozone hole resulting from a series of stratospheric-scale volcanic eruptions in West Antarctica might have triggered rapid Antarctic de-glaciation 18 kyr ago. We propose to test the use of nitrogen isotopes of nitrate as a proxy for past surface-ultraviolet radiation levels by measuring the nitrogen isotopes of nitrate at high resolution in the top 10 m of a previously drilled shallow ice core from the South Pole. The period contained in this ice is 1950-2004 Common Era (C.E.), which will allow researchers to examine and calibrate the nitrate isotope enrichment under the well-known modern-day ozone hole. This will inform the utility of similar measurements on samples from a period of volcanism 18 kyr before present from a new ice core being drilled at the South Pole ice core over the next two years.There is no field work in Antarctica as part of this project.