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

格陵兰冰盖的稳定性对科学家和社会至关重要。总的来说，在未来海平面上升的背景下。格陵兰冰盖将在多大程度上失去质量并导致海平面上升&amp；#8232；未来几十年取决于冰川边缘的流量和地表物质平衡，即积雪和地表融化之间的平衡。格陵兰地表物质平衡的估算越来越多地利用气候再分析和高分辨率区域气候模式来确定积雪、地表融化和径流/再冻结。这些模式在格陵兰冰盖陡峭边缘显示出显著的、依赖于模式的偏差（与观测值的差异），在那里观测到的累积和表面融化速率（在空间和时间上）最高、变化最大。因此，格陵兰冰盖的边缘迫切需要更新的积累。和熔化数据来验证模型和改进质量平衡估计。研究人员建议在格陵兰岛西部的渗透区进行两次野外季节的穿越，以利用地面雷达和浅层雪芯开发连续的原位积雪和雪密度记录。研究目标包括：(1)确定近20 ~ 40年来西格陵兰岛积雪的时空分布格局；(2)评估格陵兰岛西部渗滤的地表融水再冻结和冰川融水储存；区在过去20-40年；(3)量化最新气候再分析模式及其对应的区域气候模式的累积和地表融化偏差。该项目将通过提供西格陵兰岛表面质量平衡的质量增加（积雪）和质量损失（表面融化）组成部分的原位验证观测，促进知识和理解。自2005年以来，格陵兰冰盖的西部边缘一直在加速失去质量，这主要是由于表面质量平衡的减少。然而，区域气候模式得出的地表物质平衡趋势在该地区相差约2.5倍。模型验证所需的西格陵兰铁芯积累记录一般结束于1996-1998年，在最近一次加速质量损失之前。研究人员将利用探地雷达开发过去20-40年间西格陵兰岛积雪的连续记录，这些雷达经频繁出现的雪坑和&amp；#8232；铁芯（25-30米）进行化学分析。他们还建议使用多偏移雷达方法来计算连续光密度&amp；#8232；数据，提供了一种方法来评估过去的表面融化，再冻结和目前的融水储存。在冰川含水层。融水再冻结在区域气候中显示出最大的变化。表面质量平衡组分之间的模型，因此验证观测是非常必要的。穿越路线将纵横交错的渗透区，几乎平行于最陡的积累和表面融化梯度，这将增加数据集的价值，用于模型验证。导线将重叠以前的导线路线，并重新占用以前采样的地点，以更新18-20年的岩心积累记录。此外，该项目将从低海拔数据贫乏地区的新站点收集核心，这些地区的积累和地表融化都增加，最需要区域气候模型验证。几种气候再分析模型的地表质量平衡验证将导致更准确的评估。当前和未来格陵兰冰盖物质平衡趋势的数据，这对准确预测至关重要。未来海平面上升。该项目将整合研究与学生&amp；#8232；多层次学习，强调来自代表性不足群体的学生的参与。该项目将资助四名研究生，并包括通过达特茅斯女性科学项目和本科生地球科学联盟多样性等成功项目招募的众多本科生研究人员。K-12学生将通过基于探究的网络气候课程，结合缅因大学的气候再分析仪和环境变化模型，以及在博伊西山脉的以雪科学为重点的实地项目，参与到这个项目中来。除了通过各自的公共事务办公室进行频繁的公开演讲和媒体采访外，pi还将通过已建立和成功的项目，如每月一次的上谷科学酒吧和两年一次的爱达荷州探索中心雪日，继续积极开展公众宣传活动。

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.