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

总的来说，该奖项旨在探索过去千年中可能发生的水气候变化，以应对厄尔尼诺-南方涛动(ENSO)平均状态的变化。通过推动美国东北太平洋地区过去1000年冰芯积累记录的时空网络的发展，这项研究将有助于更好地理解区域水文对耦合的ENSO系统的响应。研究人员提出了一种假说，即从中世纪气候异常(MCA)期间的持续类拉尼娜状态转变为小冰期(LIA)期间的持续类厄尔尼诺状态。研究小组将通过重建和评估跨越MCA-LIA过渡的东北太平洋地区的空间降水异常模式来检验这一假设。他们的假设建立在现代观测的基础上，这些观测表明，在拉尼娜(El Nino)条件下，该地区沿海-内陆降水梯度增强(较弱)。研究人员预测，在MCA-LIA过渡期间，东北太平洋降水异常模式将减弱。该项目将支持一名早期职业科学家，为本科生和研究生提供支持，并通过PolarTREC计划与K-12教师和学生进行接触。PolarTREC计划是美国国家科学基金会资助的项目，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纳入K-12课程。就促进这一科学领域的知识状况而言，拟议科学的潜在投资回报很高，早期职业科学家的支持和该提议的外展方面对NSF的任务和任务很重要。在过去的十年里，研究人员一直在美国东北太平洋开发一个冰芯阵列，目标是这一降水偶极子的两个节点(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，从山上采集了两个从地表到基岩210米的冰芯。德纳利国家公园的猎人。以确定山上的降水变率。在过去的千年里，研究人员将依靠一套支持性的地球物理数据来约束三维有限元数值模型中的冰川几何形状、速度、边界条件和流变性。组合的观测和模型数据集将允许团队消除冰流(导致雪层变薄)和积雪速率的空间变异性的影响，以估计两个冰芯的时间积雪变异性。亨特说，人们对沿海圣埃利亚斯山脉冰核遗址(PR Col、NW Col、洛根山King Col和日食冰场)的地球物理特征知之甚少，这些地点是在地球物理技术和数值模拟能力最近取得进展之前于2002年钻探的。这种信息的缺乏将在圣伊利亚山和圣伊利亚山的任何比较中引入错误。因此，研究小组特别建议通过收集圣埃利亚斯山脉现有冰芯地点的新地球物理数据来改进基于冰芯的堆积记录，从而改善过去一千年来东北太平洋的水气候重建。科学目标是：1)绘制日食冰原、科尔王和科尔山的基岩地形图。这些数据包括：2)确定所有站点的地表速度；3)绘制近地表空间累积速率模式图；4)追踪所有站点的内部等时线；5)估计冰变形对层变薄的影响；6)产生更新的、至2016年的和校正的所有站点的累积时间序列；以及7)比较修正后的山体累积记录。亨特和圣埃利亚斯站点，以评估过去千年的空间降水模式。这一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.