Shrinking sea ice - reconstructions from ice cores

海冰在调节气候方面起着至关重要的作用。卫星观测显示，南极海冰正处于40年来的最低水平。在毗邻南极半岛的别林斯高晋海，海冰减少伴随着表面温度的升高和冰的加速流失。这些变化对全球海平面有直接影响，因此了解海冰减少的意义及其在调节区域气候中的作用具有全球意义。然而，对南极海冰的观测仅限于卫星时代（1970年后），气候模型很难捕捉到观测到的趋势。长期观测的缺乏阻碍了我们将最近的变化置于自然变率背景下的能力，或者为预测未来气候变化的气候模型提供现实的边界条件。冰芯中所含的海盐和其他化学物质提供了在仪器使用期之后重建海冰的最佳方法。分析能力的进步，加上新的沿海南极冰芯的收集，提供了一个独特的机会，开发新的海冰代理和生产的第一个区域重建超过百年的时间尺度。该项目的目标是重建过去200-300年来关键海洋部门的区域海冰。有机化合物，如脂肪酸，已被提议作为海冰的新替代物[1]。与现有的海冰代理[2]一起，我们现在有可能产生多代理重建。该项目将测量来自南极洲沿海和亚南极岛屿的一些冰芯中的新有机化合物。将对照溴化物和钠等无机物类对数据进行评价，以调查海冰在不同季节（夏季/冬季）和条件（第一年或多年海冰）下的变化。分析方面由化学迁移模型补充，以了解化学物种的来源和迁移途径[3]。这超越了最先进的水平，提供了一个强大的方法来校准海冰代理。学生将在-20 ℃的低温实验室和100级洁净室中对现有和计划中的南极冰芯进行有机和无机分析。样品将在化学系进行预浓缩和分析，采用项目小组开发的经过验证的方法。该项目不依赖于新的冰芯的收集;但是我们将努力让学生参与未来的钻探项目。在进行分析工作的同时，学生将使用大气扩散模型和化学传输模型进行实验，以更好地了解控制测量的化学特征的过程，并对冰芯位置沉积的气溶胶源进行指纹识别。考虑到海冰表面的重要排放，化学传输模型现已优化，可模拟冰芯的海盐浓度，该模型将用于测试传输效率和排放强度等过程的相对影响。根据学生的兴趣，有机会增加新的能力来模拟溴化物，MSA和其他有机物种的大气传输和化学。

Sea ice plays a vital role in modulating climate. Satellite observations reveal that Antarctic sea ice is at its lowest in 40 years. In the Bellingshausen Sea, adjacent to the Antarctic Peninsula, sea ice decline has been accompanied by warming surface temperatures and accelerated ice loss. These changes have a direct impact on global sea levels and thus understanding the significance of sea ice decline, and its role in modulating regional climate, is of global significance. However, observations of Antarctic sea ice are limited to the satellite era (post 1970) and climate models struggle to capture the observed trends. The lack of long-term observations is hindering our ability to place the recent changes in the context of natural variability or provide realistic boundary conditions for climate models tasked with predicting future climate change. Sea salts and other chemical species contained in ice cores provide the optimum method of reconstructing sea ice beyond the instrumental period. Advances in analytical capability, together with the collection of new coastal Antarctic ice cores, provides a unique opportunity to develop novel sea ice proxies and produce the first regional reconstructions over centennial timescales. The goal of this project is to produce regional sea ice reconstructions in key ocean sectors over the past 200-300 years. Organic compounds, such as fatty acids, have been proposed as a new proxy for sea ice [1]. Together with existing sea ice proxies [2], we now have the potential to produce multi-proxy reconstructions. This project will measure new organic compounds from a number of ice cores from coastal Antarctica and the sub-Antarctic islands. The data will be evaluated against inorganic species, such as bromide and sodium, to investigate changes in sea ice during different seasons (summer/ winter) and conditions (first-year or multi-year sea ice). The analytical aspect is complemented by chemical transport modelling to understand the source and transport pathways of chemical species [3]. This goes beyond the state-of-the-art by providing a robust method to calibrating sea ice proxies. The student will sub-sample existing and planned Antarctic ice cores for organic and inorganic analysis, in the -20C cold laboratories and class-100 cleanroom. The samples will be pre-concentrated and analysed at the Department of Chemistry, following a proven method developed by the project team. The project is not dependent on the collection of new ice cores; however we will endeavour to include the student in future drilling projects.In parallel to this analytical work, the student will carry out experiments using an atmospheric dispersion model and a chemical transport model to better understand the processes controlling the chemical signatures measured and fingerprint the source of aerosol deposited at ice core locations. The chemical transport model, now optimised to simulate sea salt concentrations of ice cores taking into account important emissions from the sea ice surface, will be used to test the relative influence of processes such as transport efficiency and emissions strength. Depending on the student's interests, there are opportunities to add new capability to simulate the atmospheric transport and chemistry of bromide, MSA and other organic species.