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

格陵兰冰盖（GrIS）中有足够的水，如果它融化，它将显著提高大多数沿海城市的海平面，对社会产生巨大影响。面对加速的冰盖对海平面上升的贡献，仍然不确定GrIS将如何适应北极变暖，海冰减少和相关的降水模式变化。这是一个令人关切的问题，因为未来海平面上升在很大程度上取决于GrIS对北极变化的反应。科学界目前尚未决定是在温暖时期大大减少的动态GrIS模型，还是即使在比今天更温暖的时期也相对稳定的模型。该提案提出了这样一个想法，即北极降水量增加抵消了GrIS在温度升高期间的质量损失。研究人员将通过在过去和正在进行的温暖时期提供有关北极系统变化和相关GrIS动态的重要新信息来测试这一点，并采用冰盖建模工作来合成针对过去和未来GrIS模拟的所有新数据。研究人员明确地将联合收割机多个科学学科结合起来，以更好地了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。该项目将培养6名研究生和1名博士后研究员。跨领域的研究计划是由外联计划的范围，以开发各种可交付成果，包括开发一个iBook和公共外联活动。此外，该小组还将参加在布法罗和纽约市举行的公共外联活动，在那里，公众和科学家在一个休闲的环境中互动。最后，这项工作与美国航天局正在进行的任务和国家科学基金会内的其他方案具有协同作用。格陵兰冰盖和海冰构成了北极冰冻圈最大和最重要的组成部分。北极降水增加可以抵消GrIS质量损失的假设，在温度升高的时候，源于最近的研究结果表明，它可能比预期的更稳定，在间冰期。研究人员将：在中全新世热盛期和自热盛期以来产生新的GrIS边缘重建（9，000至5，000年前），采用了一种强有力的方法，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;开发新的全新世气候湿度重建，湖泊和海洋沉积物的温度和海冰状况，以及现有北极冰芯和其他古气候数据的高级综合;并采用最先进的数值冰盖模拟由冰缘和气候重建，以测试一系列的气候和动态控制GrIS变化。如果这一观点得到支持，那么它将表明在温暖时期有一个相对稳定的GrIS。然而，如果该项目提供的证据表明，GrIS在温暖的比现在的全新世中期大幅撤退，反过来，GrIS的反应更敏感的温度比降水量的变化，结果将支持一个紧密耦合的冰盖大小温度的链接，反过来，一个更大的近期GrIS海平面上升的贡献。无论哪种结果，都将对北极系统的命运、全球气候信息系统和全球海平面上升产生根本性的影响。

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.