Collaborative Research: GreenTrACS: a Greenland Traverse for Accumulation and Climate Studies

合作研究：GreenTrACS：用于积累和气候研究的格陵兰穿越

• 批准号: 1417678
• 负责人: Erich Osterberg
• 金额: $ 59.67万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1417678&HistoricalAwards=false
• 关键词: Collaborative; Research; GreenTrACS; Greenland; Traverse

The stability of the Greenland Ice Sheet is of critical interest to scientists and society
at large in the context of future sea-level rise. The extent to which the Greenland Ice Sheet will lose mass and contribute to rising sea level
in the coming decades depends on the discharge from glaciers at its edges and on the surface mass balance, which is the balance between snow accumulation and surface melt. Estimates of Greenland surface mass balance increasingly utilize climate reanalyses and high-resolution regional climate models to determine snow accumulation, surface melt and runoff/refreeze. These models show significant, and model-dependent, biases (differences from observations) along the steep edges of the Greenland Ice Sheet where the highest and most variable (in space and time) rates of accumulation and surface melt are observed. Thus, the edges of the Greenland Ice Sheet are in critical need of updated accumulation
and melt data to validate models and improve mass balance estimates. The investigators propose a traverse in the Western Greenland percolation zone over two field seasons to develop continuous in-situ snow accumulation and firn density records using ground-based radar and shallow firn cores. The research objectives include: (1) determining the patterns, in time and space, of snow accumulation in Western Greenland over the past 20-40 years; (2) evaluating surface melt refreeze and englacial meltwater storage in the Western Greenland percolation
zone over the past 20-40 years; and (3) quantifying the accumulation and surface melt biases of the most recent climate reanalysis models and their regional climate model counterparts.This project will advance knowledge and understanding by providing in-situ validation observations for both the mass gain (snow accumulation) and mass loss (surface melt) components of Western Greenland surface mass balance. The western edge of the Greenland Ice Sheet has been losing mass at an accelerating rate since 2005, due mostly to decreasing surface mass balance. However, surface mass balance trends derived from regional climate models differ by a factor of ~2.5 in this region. Western Greenland firn core accumulation records, required for model validation, generally end in 1996-1998, before the most recent period of accelerated mass loss. The investigators will develop continuous records of Western Greenland snow accumulation over the last 20-40 years using ground-penetrating radar validated by frequent snow pits and
firn cores (25-30 m) analyzed for chemistry. They also propose to use a multi-offset radar method to calculate continuous firn density
data, providing a means to assess past surface melt, refreeze and current meltwater storage
in glacier aquifers. Meltwater refreeze shows the largest variability in regional climate
models among surface mass balance components, and thus validation observations are critically needed. The traverse route will crisscross the percolation zone, near-parallel to the steepest accumulation and surface melt gradients, which will increase the value of the dataset for model validation. The traverse will overlap previous traverse routes and reoccupy previously sampled sites to update firn core accumulation records by 18-20 years. In addition, the project will collect cores from new sites in data-poor regions at lower elevations, where both accumulation and surface melt increase and regional climate model validation is most needed. Surface mass balance validation of several climate reanalysis models will lead to more accurate assessments
of current and future Greenland Ice Sheet mass balance trends, which is critical for accurately predicting
future sea-level rise. The project will integrate research with student
learning at multiple levels, with an emphasis on the participation of students from underrepresented groups. The project will fund four graduate students, and incorporate numerous undergraduate researchers recruited through successful programs like the Dartmouth Women in Science Project and the Diversity in Undergraduate Geoscience Alliance. K-12 students will be engaged in this project through inquiry-based, web-hosted climate lessons incorporating the University of Maine Climate Reanalyzer and Environmental Change Model, and through field-based programs in the Boise Mountains focused on snow science. The PIs will continue their active public outreach through established and successful programs like the monthly Upper Valley Science Pub and the biannual Snow Day at the Discovery Center of Idaho, in addition to their frequent public presentations and media interviews through their respective Public Affairs offices.

在未来的海平面上升的背景下，格陵兰冰盖的稳定性对科学家和社会的稳定性引起了关键。在未来几十年中，格陵兰冰盖将失去质量并导致海平面上升的效果取决于其边缘和表面质量平衡的排放，这是积雪积聚和表面融化之间的平衡。格陵兰表面质量平衡的估计越来越多地利用气候重新分析和高分辨率的区域气候模型来确定积雪，表面熔体和径流/重新冻结。这些模型显示出沿格陵兰冰盖陡峭边缘的显着且依赖模型的偏见（与观测值的差异），其中观察到了最高和最可变性的（在时空和时间）的累积速率和表面熔体的速率。因此，格陵兰冰盖的边缘迫切需要更新的积累＆＃8232;并融化数据以验证模型并改善质量平衡估计。研究人员在两个田间季节中提议在格陵兰岛西部渗透区进行遍历，以使用地面雷达和浅层岩心来发展连续的原位积雪和FIRN密度记录。研究目标包括：（1）在过去20 - 40年内确定西部格陵兰岛的积雪的模式； （2）在过去的20 - 40年中，评估西部格陵兰岛渗透区的地表熔体重新冻结和缝隙融化储存； （3）量化最新气候重新分析模型的积累和表面熔体偏差及其区域气候模型对应。该项目将通过为质量增益（积雪积累）和西部绿地表面质量平衡的质量增益（积雪）和质量增益（积雪群体损失）和质量增益（积雪群体损失）来提高知识和理解。自2005年以来，格陵兰冰盖的西部边缘一直以加速率失去质量，这主要是由于表面质量平衡的降低。但是，该区域中从区域气候模型中得出的表面质量平衡趋势差异约为2.5。模型验证所需的西部格陵兰FIR​​N核心积累记录通常在1996 - 1998年结束，在最近加速质量损失之前。研究人员将使用经频繁的雪坑验证的地面穿透雷达在过去20 - 40年内的西部绿地积雪的连续记录，并分析了对化学分析的FIRN核心（25-30 m）。他们还建议使用多偏雷达方法来计算连续的FIRN密度＆＃8232;数据，提供一种评估过去的表面熔体，重新冻结和当前的融合水存储的方法。融合重新冷冻显示了区域气候中最大的变异性＆＃8232;在表面质量平衡成分中的模型，因此非常需要验证观测值。遍布路线将跨越渗透区，接近最陡峭的积累和表面熔体梯度，这将增加数据集的值以验证模型验证。 Traverse将重叠以前的遍历路线和先前对站点的重新占领，以将FIRN核心积累记录更新18-20年。此外，该项目将在较低海拔的数据贫困区域的新地点收集核心，其中最需要积累和表面熔体增加和区域气候模型验证。几种气候重新分析模型的表面质量平衡验证将导致更准确的评估＆＃8232;当前和未来的格陵兰冰盖质量平衡趋势，这对于准确预测未来的海平面上升至关重要。该项目将将研究与学生多个级别学习，重点是来自代表性不足小组的学生的参与。该项目将为四名研究生提供资金，并通过成功的计划招募众多本科生研究人员，例如达特茅斯妇女在科学项目中和本科生地球科学联盟的多样性。 K-12学生将通过纳入缅因州的气候重新分析仪和环境变化模型的基于询问的，网络托管的气候课程，以及通过Boise Mountains的基于现场的计划来参与该项目。除了通过各自的公共事务办公室进行频繁的公开介绍和媒体访谈，PI将通过既定而成功的计划，例如每月的上谷科学酒吧和双年度降雪日，以及双年度降雪日，继续他们的公众宣传。