The Taylor Glacier, Antarctica, Horizontal Ice Core: Exploring changes in the Natural Methane Budget in a Warming World and Expanding the Paleo-archive

This award supports a project to use the Taylor Glacier, Antarctica, ablation zone to collect ice samples for a range of paleoenvironmental studies. A record of carbon-14 of atmospheric methane (14CH4) will be obtained for the last deglaciation and the Early Holocene, together with a supporting record of CH4 stable isotopes. In-situ cosmogenic 14C content and partitioning of 14C between different species (14CH4, C-14 carbon monoxide (14CO) and C-14 carbon dioxide (14CO2)) will be determined with unprecedented precision in ice from the surface down to ~67 m. Further age-mapping of the ablating ice stratigraphy will take place using a combination of CH4, CO2, and delta 18O of oxygen gas and H2O stable isotopes. High precision, high-resolution records of CO2, delta 13C of CO2, nitrous oxide (N2O) and N2O isotopes will be obtained for the last deglaciation and intervals during the last glacial period. The potential of 14CO2 and Krypton-81 (81Kr) as absolute dating tools for glacial ice will be investigated. The intellectual merit of proposed work includes the fact that the response of natural methane sources to continuing global warming is uncertain, and available evidence is insufficient to rule out the possibility of catastrophic releases from large 14C-depleted reservoirs such as CH4 clathrates and permafrost. The proposed paleoatmospheric 14CH4 record will improve our understanding of the possible magnitude and timing of CH4 release from these reservoirs during a large climatic warming. A thorough understanding of in-situ cosmogenic 14C in glacial ice (production rates by different mechanisms and partitioning between species) is currently lacking. Such an understanding will likely enable the use of in-situ 14CO in ice at accumulation sites as a reliable, uncomplicated tracer of the past cosmic ray flux and possibly past solar activity, as well as the use of 14CO2 at both ice accumulation and ice ablation sites as an absolute dating tool. Significant gaps remain in our understanding of the natural carbon cycle, as well as in its responses to global climate change. The proposed high-resolution, high-precision records of delta 13C of CO2 would provide new information on carbon cycle changes both during times of rising CO2 in a warming climate and falling CO2 in a cooling climate. N2O is an important greenhouse gas that increased by ~30% during the last deglaciation. The causes of this increase are still largely uncertain, and the proposed high-precision record of N2O concentration and isotopes would provide further insights into N2O source changes in a warming world. The broader impacts of proposed work include an improvement in our understanding of the response of these greenhouse gas budgets to global warming and inform societally important model projections of future climate change. The continued age-mapping of Taylor Glacier ablation ice will add value to this high-quality, easily accessible archive of natural environmental variability. Establishing 14CO as a robust new tracer for past cosmic ray flux would inform paleoclimate studies and constitute a valuable contribution to the study of the societally important issue of climate change. The proposed work will contribute to the development of new laboratory and field analytical systems. The data from the study will be made available to the scientific community and the broad public through the NSIDC and NOAA Paleoclimatology data centers. 1 graduate student each will be trained at UR, OSU and SIO, and the work will contribute to the training of a postdoc at OSU. 3 UR undergraduates will be involved in fieldwork and research. The work will support a new, junior UR faculty member, Petrenko. All PIs have a strong history of and commitment to scientific outreach in the forms of media interviews, participation in filming of field projects, as well as speaking to schools and the public about their research, and will continue these activities as part of the proposed work. This award has field work in Antarctica.本项目获此资助，将利用南极洲泰勒冰川（Taylor Glacier）消融区采集冰芯样本，用于一系列古环境研究。研究将获取末次冰消期及早全新世的大气甲烷碳十四（¹⁴CH₄）记录，并配套获取甲烷稳定同位素记录。研究人员将以前所未有的精度，对从地表至约67米深度的冰芯，测定其中的原地宇宙成因碳十四（in-situ cosmogenic ¹⁴C）含量，以及不同碳十四物种（¹⁴CH₄、碳十四一氧化碳（¹⁴CO）与碳十四二氧化碳（¹⁴CO₂））的分配比例。研究将结合甲烷、二氧化碳以及氧气与水的稳定同位素δ¹⁸O，对正在消融的冰地层开展进一步的年龄填图。本研究将获取末次冰消期及末次冰期部分时段的二氧化碳、二氧化碳δ¹³C、一氧化二氮（N₂O）及其同位素的高精度高分辨率记录，并将探索¹⁴CO₂与氪-81（⁸¹Kr）作为冰川冰绝对定年工具的潜力。本研究的科学价值在于，当前天然甲烷源对持续全球变暖的响应尚不明确，且现有证据不足以排除大型贫¹⁴C储层（如甲烷水合物与永久冻土）发生灾难性释放的可能性。本研究提出的古大气¹⁴CH₄记录，将增进我们对气候大幅变暖期间此类储层释放甲烷的可能规模与时间的理解。目前学界对冰川冰中的原地宇宙成因碳十四（不同机制下的生成速率及物种间分配比例）仍缺乏全面认知。此类认知的完善，将有望实现利用冰积累区冰芯中的原地¹⁴CO作为可靠且简便的古宇宙射线通量示踪剂，进而反演古太阳活动；同时也可将冰川冰积累区与消融区的¹⁴CO₂用作绝对定年工具。当前学界对自然碳循环及其对全球气候变化的响应仍存在显著认知空白。本研究提出的二氧化碳δ¹³C高分辨率高精度记录，将为气候变暖期二氧化碳上升阶段与气候变冷期二氧化碳下降阶段的碳循环变化提供新的研究数据。一氧化二氮（N₂O）是一类重要的温室气体，在末次冰消期期间浓度上升了约30%，其浓度上升的成因目前仍未完全明确；本研究提出的一氧化二氮浓度与同位素高精度记录，将为变暖背景下一氧化二氮的源变化提供进一步的认知。本研究的社会价值包括：增进我们对这些温室气体收支对全球变暖响应的理解，并为具有重要社会意义的未来气候变化模型预测提供参考；对泰勒冰川消融冰的持续年龄填图，将为这一高质量、易于获取的自然环境变化档案增添研究价值；将¹⁴CO确立为可靠的古宇宙射线通量新型示踪剂，将为古气候研究提供参考，并为关乎社会福祉的气候变化研究作出宝贵贡献。本研究将助力新型实验室与现场分析系统的开发。本研究产生的数据将通过国家冰雪数据中心（NSIDC）与美国国家海洋和大气管理局（NOAA）古气候数据中心向科学界及广大公众开放。罗切斯特大学（UR）、俄亥俄州立大学（OSU）与斯克里普斯海洋研究所（SIO）将各培养1名研究生，本研究还将助力俄亥俄州立大学（OSU）1名博士后的培养。另有3名罗切斯特大学（UR）本科生将参与野外工作与研究。本研究将支持罗切斯特大学（UR）新任初级教职人员佩特连科（Petrenko）的工作。所有项目负责人（PIs）均有丰富的科学科普经历，并致力于通过媒体采访、参与野外项目拍摄、向学校与公众讲解其研究成果等形式开展科普工作，且将在本研究中继续开展此类活动。本资助项目包含南极洲野外工作。