Collaborative Research: Sediment and Stability: Quantifying the Effect of Moraine Building on Greenland Tidewater Glaciers

格陵兰冰盖（GrIS）是目前对海平面上升的最大贡献，最近超过了高山冰川和冰帽、南极冰盖和陆地蓄水的贡献。质量损失集中在冰盖的外围，在那里低洼的出风口冰川流入格陵兰岛周围温暖的海洋。尽管总体质量损失，格陵兰冰盖的出口冰川在卫星时代观测到的冰川锋退缩量方面经历了显著的变化。这种变化仍然无法解释，因为有许多过程可以影响出口冰川锋面的位置，而这些环境很难获得观测结果。该项目旨在收集格陵兰岛三个出口冰川前缘的观测数据，这些冰川已观测到退缩变异性。该项目的目标是确定冰-海边界沉积物的沉积是否导致了观测到的冰川退缩的变化。此外，该项目将测量活跃冰川前沿存在的沉积过程的速率和类型，以及卫星记录中观测到的每个冰川的过去位置。该项目还将对可能导致冰川间沉积速率变化的冰川基本参数进行观测。该项目的总体目标是通过关注系统中一个知之甚少、观测有限的部分：沉积物预算，来了解冰盖变化和稳定的基本驱动因素。在冰川末端形成的冰碛可能比在没有沉积物的情况下形成更大的稳态冰川，这在高融水环境（如阿拉斯加）中是很明显的。然而，对前冰期沉积的过程和速率知之甚少，特别是在格陵兰岛，那里有丰富的冰岸，但冰岸形成对冰盖动力学的影响是不受限制的。这个项目的中心假设是，对一些冰川系统来说，道义上的河岸沉积可以稳定或延缓退缩。该项目将通过对四个过程的观察来验证这一假设，这四个过程有助于在三个相邻的格陵兰冰川上形成冰碛，这些冰川具有截然不同的动态历史和几何形状。该项目将部署一种新型远程操作工具（ROV Nereid），用于在深海冰缘环境中进行测量和采样，以获得冰-沉积物-海洋界面的高分辨率地质、地球物理和海洋学测量。该项目将培养研究生，重点是指导和多样化的地球科学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Greenland Ice Sheet (GrIS) is presently the largest contributor of added mass to rising sea levels, recently surpassing contributions from alpine glaciers and ice caps, the Antarctic Ice Sheet and land water storage. Mass loss is concentrated at the periphery of the ice sheet where low-lying outlet glaciers drain into the warm ocean surrounding Greenland. Despite overall mass loss, outlet glaciers of the Greenland Ice Sheet have experienced significant variability in the amount of glacier-front retreat observed over the satellite era. This variability remains unexplained because there are many processes that can influence the position of the front of an outlet glacier and these environments are difficult to obtain observations in. This project aims to collect observations from the front of three outlet glaciers in Greenland where retreat variability has been observed. The goal of this project is to determine if the deposition of sediment at the ice-ocean boundary is responsible for the observed variability in glacier retreat. Further, this project will measure the rates and types of sedimentation processes present at the active glacier front as well as the past position of each glacier observed in the satellite record. The project will also take observations of basic glacier parameters that may be responsible for variations in the rates of sedimentation between glaciers.The overarching goal of this project is to understand the fundamental drivers of ice sheet change and stability through focusing on a poorly understood, observation-limited part of the system: the sediment budget. Moraine building at glacier termini may enable larger steady-state glaciers than would be possible in the absence of sediment, as is evident in high-meltwater settings (e.g., Alaska). However, processes and rates of proglacial sedimentation are poorly known, especially in Greenland, where morainal banks are abundant but where the influence of bank formation on ice sheet dynamics is unconstrained. The central hypothesis of this project is that morainal bank sedimentation can stabilize or delay retreat for some glacier systems. This project will test this hypothesis with observations of four processes that contribute to moraine building at three neighboring Greenland glaciers with sharply different dynamic histories and geometries. The project will deploy a novel remotely operated vehicle (ROV Nereid) designed for surveying and sampling in deep, ice marginal environments to obtain high-resolution geological, geophysical, and oceanographic measurements at the ice-sediment-ocean interface. This project will train graduate students, with a focus on mentorship and diversifying the geosciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.