P2C2: Geophysical Reconnaissance to Expand Ice Core Hydroclimate Reconstructions in the Northeast Pacific

一般来说，该奖项旨在探索过去千年来可能因厄尔尼诺-南方涛动（ENSO）平均状态变化而发生的水文气候变化。 通过推动美国东北太平洋地区过去一千年冰芯积累记录时空网络的发展，这项研究将有助于更好地理解区域水文对耦合ENSO系统的响应。研究人员建议调查这样一种假设，即在中世纪气候异常（MCA）期间，持续的拉尼娜状态发生了变化小冰河时期（LIA）的持续厄尔尼诺状态。 研究小组将通过重建和评估跨MCA-LIA过渡的东北太平洋空间降水异常模式来验证这一假设。 他们的假设是建立在现代观测的基础上的，现代观测表明，在拉尼娜（厄尔尼诺）条件下，该地区沿海-内陆降水梯度增强（减弱）。 研究人员预测，东北太平洋降水异常模式将在MCA-LIA过渡期间减弱。该项目将支持早期职业科学家，为本科生和研究生提供支持，并通过PolarTREC计划向K-12教师和学生进行推广，NSF资助的一个项目，旨在将K-12教师与极地研究人员联系起来，目标是将极地科学研究融入K-12课程。 在推进这一科学领域的知识水平方面，拟议科学的潜在投资回报率很高，并且该提案的早期职业科学家和外联方面的支持对NSF使命和任务很重要。研究人员已经在美国东北太平洋开发了一个冰芯阵列，该阵列以该降水偶极子的两个节点为目标（即，圣埃利亚斯山脉和阿拉斯加中部）。 最近一次冰芯采集是在2013年，从Mt.德纳利国家公园的猎人。为了确定降水量的变化在山。亨特网站在过去的一千年里，研究人员将依靠一套支持地球物理数据，以约束冰川的几何形状，速度，边界条件和流变特性的三维有限元数值模型。结合观测和模型数据集将使团队能够消除冰流（导致层变薄）和雪积累率的空间变异性的影响，以估计两个冰芯的时间积累变异性。亨特，很少有人知道沿海圣埃利亚斯山脉冰芯网站（PR山口，西北山口，国王山口的洛根山和日食冰原），这是在2002年钻探地球物理技术和数值模拟能力的最新进展之前的地球物理特征。 这种信息的缺乏将引入错误的任何比较圣埃利亚斯和山。亨特积累记录，从而评估的MCA-LIA过渡hypothesis.Consequently，研究小组特别提出，以改善冰芯为基础的积累记录，因此水文气候重建在过去的千年，在东北太平洋通过收集新的地球物理数据在现有的冰芯网站在圣埃利亚斯范围。科学的目标是：1）制定基岩地形图的日食冰原，国王山口，山。洛根峰顶高原2）确定所有站点的表面速度; 3）绘制近地表空间累积速率模式; 4）跟踪所有站点的内部等时线; 5）估计冰变形对地层变薄的影响; 6）生成更新的，到2016年，所有站点的校正累积时间序列; 7）比较Mt.亨特和圣埃利亚斯网站，以评估空间降水模式在过去的千年。研究战略需要使用最先进的探地雷达（GPR），地球化学，卫星遥感，数值模拟和数据合成技术。

Generally, this award aims to explore hydroclimate changes over the past Millennium that possibly occurred in response to changes in the mean state of the El Nino-Southern Oscillation (ENSO). By advancing the development of a spatial-temporal network of ice core accumulation records covering the past millennium in the NE Pacific region of the United States, this research will foster a greater understanding of regional hydrologic response to the coupled ENSO system.The researchers propose to investigate the hypothesis that a change occurred from a persistent La Nina-like state during the Medieval Climate Anomaly (MCA) to a persistent El Nino-like state during the Little Ice Age (LIA). The research team will test this hypothesis by reconstructing and evaluating the spatial precipitation anomaly pattern in the Northeast Pacific across the MCA-LIA transition. Their hypothesis is founded on modern observations that show an enhanced (weaker) coastal-inland precipitation gradient in the region during La Nina (El Nino) conditions. The researchers predict that the NE Pacific precipitation anomaly pattern will weaken across the MCA-LIA transition.The project will support an early career scientist, provide support for undergraduate and graduate students, and enable outreach to K-12 teachers and students through the PolarTREC program, an NSF funded program which seeks to link K-12 teachers with Polar researchers with a goal of integrating polar science research into K-12 curriculum. The potential return on investment of the proposed science is high in terms of advancing the state of knowledge in this area of science and the support of early career scientists and outreach aspects of the proposal are important to the NSF Mission and mandate.For the past decade, the researchers have been developing an ice core array in the NE Pacific of the United States that targets the two nodes of this precipitation dipole (i.e., St. Elias Range and Central Alaska). The most recent ice core acquisition was in 2013 with the recovery of two surface-to-bedrock 210-meter ice cores from Mt. Hunter in Denali National Park. To determine precipitation variability at the Mt. Hunter site over the past millennium, the researchers will rely on a suite of supporting geophysical data to constrain glacier geometry, velocity, boundary conditions, and rheological properties in a 3-dimensional finite element numerical model. The combined observational and model datasets will allow the team to remove influences of ice flow (which causes layer thinning) and spatial variability in snow accumulation rate to estimate temporal accumulation variability from the two ice cores.In contrast to Mt. Hunter, little is known about the geophysical characteristics of the coastal St. Elias Range ice core sites (PR Col, NW Col, King Col on Mt Logan and the Eclipse Icefield), which were drilled in 2002 prior to recent advances in geophysical techniques and numerical modeling capability. This lack of information would introduce error in any comparison of the St. Elias and Mt. Hunter accumulation records, and thus evaluation of the MCA-LIA transition hypothesis.Consequently, the research team specifically proposes to improve ice core-based accumulation records, and therefore hydroclimate reconstructions for the past millennium, in the NE Pacific through the collection of new geophysical data at existing ice core sites in the St. Elias Range. The science objectives are to: 1) develop bedrock topography maps of the Eclipse Icefield, King Col, and Mt. Logan summit plateau sites; 2) determine surface velocities at all sites; 3) map near-surface spatial accumulation rate patterns; 4) trace internal isochrones at all sites; 5) estimate ice deformation effects on layer thinning; 6) produce updated, to 2016, and corrected accumulation time series at all sites; and 7) compare corrected accumulation records from the Mt. Hunter and St. Elias sites to evaluate spatial precipitation patterns over the past millennium. The research strategy necessitates the use of state-of-the-art ground penetrating radar (GPR), geochemical, satellite remote sensing, numerical modeling, and data synthesis techniques.