Collaborative Research: Ice sheet sensitivity in a changing Arctic system - using data and modeling to test the stable Greenland Ice Sheet hypothesis

非技术性格陵兰冰盖(GRIS)中有足够的水，如果它融化，将显著提高大多数沿海城市的海平面，给社会带来巨大的后果。面对冰盖对海平面上升的加速贡献，GRIS将如何适应北极变暖、海冰减少和相关的降水模式变化仍然是不确定的。这是一个令人担忧的问题，因为未来海平面的上升在很大程度上取决于全球海洋观测系统对北极变化的反应。科学界目前还没有做出决定，是建立一个在暖期大幅减少的动态地球引力指数模型，还是建立一个相对稳定的模型，即使是在比现在更暖和的时期。这项提议提出的观点是，北极降水的增加抵消了全球变暖系统在高温时期的质量损失。研究人员将通过在过去和正在进行的暖期期间提供关于北极系统变化和相关的GRIS动力学的重要新信息，并利用冰盖模拟工作合成针对过去和未来GRIS模拟的所有新数据来测试这一点。研究人员明确地将多个科学学科结合在一起，以更好地理解北极系统的关键组成部分，如降水、温度、海冰覆盖和GRIS质量平衡是如何相互联系的。这个项目将培养6名研究生和1名博士后研究人员。这项研究结果将与北极系统、全球海平面上升和全球海平面上升的命运密切相关。交叉研究计划与外联计划的范围相平行，以开发各种可交付成果，包括开发电子书和公共外联活动。此外，该团队还将参加布法罗和纽约市的公共外展活动，公众和科学家在那里进行随意的互动。最后，这项工作与NASA正在进行的任务和国家科学基金会内的其他项目具有协同作用技术由于格陵兰岛数值冰盖模型和新的次冰层地形的最新进展，结合微调的野外方法和地质年代学技术，关注北极变暖的冰冻圈变化的协调、跨学科努力的时机已经成熟；格陵兰冰盖(GRIS)和海冰构成北极冰冻圈最大和最关键的组成部分。北极降雨量的增加可以抵消在气温升高期间的GRIS质量损失，这一假说源于最近的发现，表明在间冰期，GRIS可能比预期的更稳定。研究人员将：在全新世中期最热时期(9000至5000年前)及其以来重建新的GRIS边缘，采用将湖泊沉积物地层学与新的冰下地形和新的高灵敏度宇宙成因同位素方法相结合的强大方法；开发新的全新世气候，从湖泊和海洋沉积物中重建水分、温度和海冰条件，并先进地综合现有北极冰芯和其他古气候数据；以及使用最先进的冰盖数值模拟，以测试一系列对GRIS变化的气候和动态控制。如果这一想法得到支持，那么它将意味着在暖期有一个相对稳定的GRI。然而，如果该项目提供的证据表明，在比现在更暖和的中期全新世期间，GRIS显著后退，反过来，GRIS对温度的反应比对降水变化更敏感，那么结果将支持一个紧密耦合的冰盖大小-温度联系，反过来，GRIS对海平面上升的短期贡献要大得多。这两种结果都将对北极系统、全球海洋观测系统和全球海平面上升的命运产生根本性的影响。

NontechnicalThere is enough water in the Greenland Ice Sheet (GrIS) that, were it to melt, it would raise sea level in most coastal cities significantly with huge consequences for society. In the face of accelerated ice sheet contribution to sea level rise, it remains uncertain how the GrIS will adjust to a warming Arctic, declining sea ice and related changing precipitation patterns. This is a concern, given that future sea level rise is strongly dependent on the GrIS response to arctic change. The scientific community is currently undecided between a model of a dynamic GrIS that becomes greatly reduced during warm periods and a model where it is relatively stable, even through periods warmer than today. This proposal addresses the idea that increased arctic precipitation offsets GrIS mass loss during times of elevated temperature. The researchers will test this by contributing significant new information on arctic system change and related GrIS dynamics during past and ongoing warm periods, and employing an ice sheet modeling effort synthesizing all new data aimed at both past and future GrIS simulations. The researchers explicitly combine multiple scientific disciplines to provide a better understanding of how key arctic system components such as precipitation, temperature, sea-ice cover and GrIS mass balance are interconnected. The results will be of fundamental relevance to the fates of the arctic system, the GrIS and global sea level rise.This project will train six graduate students and one post-doctoral researcher. The cross-cutting research program is paralleled by the scope of the outreach plan, to develop a variety of deliverables, including development of an iBook and public outreach events. In addition the team will participate in public outreach events in Buffalo and New York City, where the public and scientists interact in a casual setting. Finally, this work has synergies with ongoing missions at NASA and other programs within the NSF.TechnicalDue to recent advances in numerical ice sheet models and new sub-ice topography of Greenland, combined with finely-tuned field approaches and geochronologic techniques, the time is ripe for a coordinated, cross-disciplinary effort focusing on cryosphere variability in a warming Arctic; the Greenland Ice Sheet (GrIS) and sea ice constitute the largest, and most critical components of the arctic cryosphere. The hypothesis that increased arctic precipitation can counterbalance GrIS mass loss during times of elevated temperatures stems from recent findings suggesting that it may be more stable than expected during interglacials. The researchers will: generate new GrIS margin reconstructions during and since the mid-Holocene Thermal Maximum (9,000 to 5,000 years ago), with a powerful approach that combines lake sediment stratigraphy with new sub-ice topography and novel high-sensitivity cosmogenic isotope methods; develop new Holocene climate reconstructions of moisture, temperature and sea ice conditions from lake and ocean sediments and an advanced synthesis of existing arctic ice core and other paleoclimate data; and employ state-of-the-art numerical ice sheet modeling fueled by ice margin and climate reconstructions to test a range of climatic and dynamic controls on GrIS change. If the idea is supported, then it would suggest a relatively stable GrIS during warm periods. If, however, this project provides evidence that the GrIS retreated considerably during the warmer-than-present mid-Holocene and in turn, that the GrIS has reacted more sensitively to temperature than to precipitation change, the results would support a tightly coupled ice sheet size-temperature link and in turn, a much greater near-term GrIS contribution to sea level rise. Either result will be of fundamental relevance to the fates of the arctic system, the GrIS and global sea level rise.