Biomass Burning, Dust, Sea Salt, Volcanic and Pollution Aerosols in the Arctic during the Last 2 Millennia: High Resolution Aerosol Records from NEEM and an Aray of Archived Ice Cores

This award will support the development and interpretation of a new generation of records of short-lived aerosols from biomass burning, dust, sea spray, volcanism, and industrial pollution in the Arctic during the past 2000 years and for selected time periods during the past >130,000 years. These objectives will be accomplished using a unique, NSF-funded analytical system developed specifically for such measurements in ice cores and recently expanded to include detailed measurements of black carbon (BC; soot) and a range of new aerosol source tracers. Proposed measurements of aerosols during the past 2000 years - building on a series of recently published findings from similar measurements in shallower ice cores - will be made on samples from a 400 m shallow core collected by Danish collaborators in 2008 and 2009 at the NorthEem (NEEM) drilling site in northern Greenland. To place the NEEM measurements in larger Arctic and global perspective, samples from a broad array of ~1000 year archived Arctic ice cores also will be analyzed and results from the Arctic measurements compared with similar century to millennial scale aerosol measurements already underway in Antarctic ice cores. Intellectual Merit: Natural changes in the Earth's climate are well documented in paleoclimate records, but the climate history provided by deep ice cores needs to be complemented by better understanding of how recent climate changes have affected different regions and relationships among high-, mid-, and lowlatitude processes. Short-lived aerosols - including those generated by wildfires - are important environmental and global climate forcing agents and, because of the snow-albedo feedback, particularly important to Arctic forcing when deposited in snow and ice. Their sources are primarily in the low- and mid-latitudes, but their impacts on the Polar Regions - poorly quantified because of the paucity of reliable, long-term measurements - are profound. The rich glaciochemical records developed from the NEEM and archived ice cores, especially when compared to similar Antarctic ice core aerosol records and the results synthesized through collaborative modeling studies, will transform global understanding of the sources and histories of short-lived BC, dust, volcanic, sea salt, and pollution aerosols and their impacts on climate forcing, ecosystems, and human health. Moreover, because wildfire emissions are one factor directly modulating GHG concentrations, the independent history of fire emissions provided by this and related Antarctic research will contribute to a quantitative interpretation of changing GHG concentrations measured in the deep NEEM and WAIS Divide ice cores. Broader Impacts: Policy decisions are guided by global climate model (GCM) predictions of climate under different scenarios of societal behavior; climate predictions are critically dependent on well-tuned, validated models. Despite large uncertainties in aerosol forcing identified by the IPCC, ice core aerosol records seldom are used in GCM calibration, parameterization, or tuning because of the limited scope and reliability of past ice core aerosol measurements. New generation aerosol measurements from this ice core analytical system are suitable and have enabled recent collaborations with the GCM community. To ensure the broadest impact of the proposed research in climate change and policy arenas (e.g., recent testimony before the U.S. Congress on short-lived pollutants and Arctic climate change), ongoing collaborations with modelers at NCAR, NOAA/GFDL and NASA/GISS will be expanded to incorporate the proposed ice core measurements into GCM studies. This proposal also directly addresses a thrust of the NSF-sponsored International Partnerships in Ice Core Sciences (IPICS) initiative - development of an array of detailed ice core records spanning the last 2000 years aimed at better understanding long-term climate records thorough improved, quantitative investigation of recent climate change and the role of human activities in climate forcing and on the environment. The NEEM project provides many national and international opportunities for education and outreach. The proposed effort will leverage these opportunities to the fullest extent and continue the long-term record of high school, undergraduate and graduate student, and post-doctoral fellow involvement in the laboratory; K-12 educational efforts; and dissemination of results through high visibility publications and outreach to the public, popular media, and policy makers.

本项目将支持开发并解读新一代气溶胶记录，该记录聚焦过去2000年以及过去13万余年中特定时段北极地区源自生物质燃烧、粉尘、海浪飞沫、火山活动与工业污染的短命气溶胶（short-lived aerosols）。
本项目目标将通过一套专为冰芯此类测量开发、且近期已扩展至可精准检测黑碳（black carbon, BC；炭黑 soot）与一系列新型气溶胶源示踪剂的独特分析系统实现，该系统由美国国家科学基金会（National Science Foundation, NSF）资助。
本次针对过去2000年气溶胶的测量工作，将基于近期在浅层冰芯中开展同类测量所获得的一系列已发表研究成果，样品取自丹麦合作团队2008至2009年在格陵兰北部北埃姆（NorthEem, NEEM）钻孔点采集的400米浅层冰芯。
为将NEEM钻孔点的测量结果置于更大范围的北极与全球视角下，研究团队还将对一批覆盖约1000年历史的存档北极冰芯样品展开分析，并将北极地区的测量结果，与南极冰芯中正在开展的、百年至千年尺度的同类气溶胶测量结果进行对比。

学术价值：
地球气候的自然变化在古气候记录中已有充分记载，但深层冰芯所提供的气候历史，仍需通过更深入理解近期气候变化如何影响不同区域，以及高、中、低纬度过程间的相互关系来加以完善。短命气溶胶——包括野火产生的气溶胶——是重要的环境与全球气候强迫因子，且由于雪反照率反馈（snow-albedo feedback）效应，当其沉降在积雪与冰面时，对北极地区的气候强迫尤为关键。这类气溶胶的源区主要集中在低纬度与中纬度地区，但其对极地地区的影响却极为深远——由于缺乏可靠的长期测量数据，这类影响此前一直未能得到精准量化。从NEEM钻孔点冰芯与存档冰芯中获取的丰富冰川化学记录，尤其是在与南极冰芯同类气溶胶记录以及协同模拟研究所得结果进行对比后，将彻底改变全球学界对黑碳（BC）、粉尘、火山气溶胶、海盐气溶胶与污染气溶胶的源区与演化历史，及其对气候强迫、生态系统与人类健康的影响的认知。此外，由于野火排放是直接调节温室气体（Greenhouse Gas, GHG）浓度的因素之一，本研究与相关南极研究所提供的独立野火排放历史，将有助于定量解读NEEM深层冰芯与西埃斯鸿沟（WAIS Divide）冰芯中测得的温室气体浓度变化。

社会影响：
政策制定需基于全球气候模型（Global Climate Model, GCM）在不同社会行为情景下的气候预测结果，而气候预测高度依赖经过调校与验证的可靠模型。尽管政府间气候变化专门委员会（Intergovernmental Panel on Climate Change, IPCC）已指出气溶胶强迫存在较大不确定性，但由于既往冰芯气溶胶测量的覆盖范围与可靠性有限，冰芯气溶胶记录极少被用于GCM的校准、参数化与调校工作。本项目所采用的新一代冰芯分析系统所产出的气溶胶测量数据，具备应用价值，且已促成与GCM研究团队的近期合作。为确保本研究在气候变化与政策领域发挥最大影响（例如近期就短命污染物与北极气候变化问题在美国国会作证），研究团队将拓展与美国国家大气研究中心（National Center for Atmospheric Research, NCAR）、美国国家海洋和大气管理局/地球物理流体动力学实验室（National Oceanic and Atmospheric Administration/Geophysical Fluid Dynamics Laboratory, NOAA/GFDL）以及美国国家航空航天局/戈达德太空研究所（National Aeronautics and Space Administration/Goddard Institute for Space Studies, NASA/GISS）建模人员的现有合作，将本次冰芯测量工作纳入GCM研究之中。本提案还直接契合美国国家科学基金会资助的国际冰芯科学伙伴关系（International Partnerships in Ice Core Sciences, IPICS）计划的核心方向——构建一系列覆盖过去2000年的高精度冰芯记录，旨在通过更完善的定量研究，深化对长期气候记录的认知，厘清近期气候变化以及人类活动在气候强迫与环境变化中所扮演的角色。NEEM项目为国内外开展教育与科普工作提供了诸多契机，本次研究将充分利用这些契机，延续长期以来的实验室学生参与机制——包括高中生、本科生、研究生与博士后研究员的参与——同时推进K12阶段的教育工作，并通过高影响力期刊论文、面向公众与大众媒体的科普以及向政策制定者的成果报送，实现研究成果的广泛传播。