Collaborative Research: Bipolar Coupling of late Quaternary Ice Sheet Variability

Timmerman/1341311该奖项支持一个项目，该项目旨在研究使北半球冰盖和南极冰盖之间的冰川尺度变化同步的物理过程。使用耦合的冰盖地球系统数值模型，研究小组将探索冰冻圈对过去温室气体浓度变化以及地球轨道和倾角变化的响应。研究人员首先捕捉每个单独冰盖对这些强迫的敏感性，然后确定它们由海平面、海洋温度和大气环流变化引起的联合变化，然后将量化本地和远程影响对长期冰量变化的相对作用。数值实验将提供更深入的物理洞察，了解过去南极冰量变化的潜在动力学及其对全球海平面的贡献。瞬变地球系统模型模拟的输出将直接与之前和正在进行的钻探工作中的冰芯数据进行比较，例如西南极冰盖(WAIS)的划分。将讨论的具体问题包括：1)与南极冰盖强迫有关的高纬度南半球大气和海洋气候是否对局部日照变化、二氧化碳、北半球变化或两者的组合做出反应？2)WAIS和东南极冰盖(EAIS)在最后一次冰川终止到全新世(21ka至今)期间是如何变化的？3)WAIS(或EAIS)是否促成了这一时期海平面的快速波动，如融水脉冲1a？4)WAIS是否在5E阶段(~125ka)完全崩溃，其时间相对于格陵兰最大退缩是什么时候？5)北半球和南半球冰盖变化的同步行为如何影响北大西洋深水和南极底水形成及其各自的倾覆单元的强度？作为该项目的一部分，进行的瞬变地球系统模型模拟将与利用冰芯、沉积物芯和陆地数据重建古气候进行密切比较。这将产生对去冰川气候变化的半球贡献、融化水脉冲的来源以及耦合冰盖气候系统中响应不同类型的强迫的潜在阈值的综合理解。要对海平面上升作出明智的长期社会反应，就需要详细了解冰盖对外部强迫的敏感性。拟议的研究将通过数值模拟和古数据分析为这一任务做出强有力的贡献。研究小组将在亚太数据研究中心(亚太数据研究中心)的网络数据服务器上提供由此产生的模型模拟，以便科学界进行进一步分析。作为该项目的一部分，一名女研究生和一名博士后研究员将接受地球系统和冰盖模型以及古气候动力学方面的培训。该奖项没有在南极洲的实地考察。

Timmerman/1341311This award supports a project to study the physical processes that synchronize glacial-scale variability between the Northern Hemisphere ice sheets and the Antarctic ice-sheet. Using a coupled numerical ice-sheet earth-system model, the research team will explore the cryospheric responses to past changes in greenhouse gas concentrations and variations in earth's orbit and tilt. First capturing the sensitivity of each individual ice-sheet to these forcings and then determining their joint variability induced by changes in sea level, ocean temperatures and atmospheric circulation, the researchers will quantify the relative roles of local versus remote effects on long-term ice volume variability. The numerical experiments will provide deeper physical insights into the underlying dynamics of past Antarctic ice-volume changes and their contribution to global sea level. Output from the transient earth system model simulations will be directly compared with ice-core data from previous and ongoing drilling efforts, such as West Antarctic Ice Sheet (WAIS) Divide. Specific questions that will be addressed include: 1) Did the high-latitude Southern Hemispheric atmospheric and oceanic climate, relevant to Antarctic ice sheet forcing, respond to local insolation variations, CO2, Northern Hemispheric changes, or a combination thereof?; 2) How did WAIS and East Antarctic Ice Sheet (EAIS) vary through the Last Glacial Termination and into the Holocene (21 ka- present)?; 3) Did the WAIS (or EAIS) contribute to rapid sea-level fluctuations during this period, such as Meltwater Pulse 1A? 4) Did WAIS collapse fully at Stage 5e (~ 125 ka), and what was its timing relative to the maximum Greenland retreat?; and 5) How did the synchronized behavior of Northern Hemisphere and Southern Hemisphere ice-sheet variations affect the strength of North Atlantic Deep Water and Antarctic Bottom Water formation and the respective overturning cells? The transient earth-system model simulations conducted as part of this project will be closely compared with paleo-climate reconstructions from ice cores, sediment cores and terrestrial data. This will generate an integrated understanding of the hemispheric contributions of deglacial climate change, the origin of meltwater pulses, and potential thresholds in the coupled ice-sheet climate system in response to different types of forcings. A well-informed long-term societal response to sea level rise requires a detailed understanding of ice-sheet sensitivities to external forcing. The proposed research will strongly contribute to this task through numerical modeling and paleo-data analysis. The research team will make the resulting model simulations available on the web-based data server at the Asia Pacific Data Research Center (APDRC) to enable further analysis by the scientific community. As part of this project a female graduate student and a postdoctoral researcher will receive training in earth-system and ice-sheet modeling and paleo-climate dynamics. This award has no field work in Antarctica.