Collaborative Research: Glacier-Ocean Interactions at a Greenland Ice Shelf at Tidal to Interannual Time Scales

合作研究：格陵兰冰架在潮汐至年际时间尺度上的冰川-海洋相互作用

基本信息

批准号：
1604076
负责人：
Andreas Muenchow
金额：
$ 36.05万
依托单位：
University of Delaware
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-08-01 至 2019-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1604076&HistoricalAwards=false
关键词：
Collaborative Research Glacier Ocean Interactions

项目摘要

The rate of ice loss at the ocean margins of the great glacial ice sheets is the largest unknown in predictions of future global sea level change. Many physical processes at a range of time and space scales determine this mass loss, but their relative roles in net loss or gain and trends are poorly understood. This project will investigate the physics of glacier-ocean interaction for a specific system, Petermann Gletscher (PG), using data to improve understanding of processes at the marine margin of PG that drains a large fraction of the Greenland Ice Sheet (GIS) into a deep fjord connected to Nares Strait via a floating, up to 1800 feet thick, ice shelf. The ice shelf has undergone significant retreat in the last few years, from 80 km long in 2010 to 50 km today. Observations of warming of the deep water in Nares Strait and Petermann Fjord, and of ice-shelf thinning during the decade preceding retreat, lead to a hypothesis that increased basal melting contributes to loss of the ice shelf. The project is motivated by three aspects of the Petermann Gletscher and Fjord system: (1) its importance as a gateway for GIS mass loss; (2) comparison of ocean dynamics in Petermann Fjord with previously studied southern Greenland systems; and (3) the value of PG as a well-constrained system for studying processes that contribute to mass loss from other northern Greenland and Antarctic ice-shelf systems and their contribution to rising global sea level. The project takes advantage of recent observations of this system, including ongoing satellite-relayed data from sub-ice-shelf moorings.This project would contribute to the development of a diverse STEM workforce through support for the training of two graduate and three undergraduate students, including a student from an under-represented group in STEM fields. The PI would continue his international collaborations with Swedish, English, and Canadian collaborators that were developed as part of the initial Petermann Gletscher study aboard I/B Oden in 2015. Outreach to the general public would be facilitated through the PI?s website, blog, occasional media interviews, and embedding national print journalists in the field work. Time series analyses will characterize how sub-glacial waters change along the central melt channel with the tides and seasons. Description of the average state and interpretation of variations will be aided by ocean survey data properties collected in the adjacent ocean by ship between 2003 and 2015. Both time- and frequency-domain statistical analyses will reveal correlation time and space scales. More specifically, Fourier, wavelet, and Hilbert transforms will be used to provide estimates of amplitude and phase at discrete scales. Frequency-domain linear system analyses will reveal input-output relations between multiple time series that represent forcings (e.g., atmospheric temperature and wind stress when sea-ice is mobile or absent, tides) and responses (e.g., depth of surface mixed layer, heat content of the meltwater plume, ice velocity and basal melt rate). Analyses of data from GPS and pressure sensors at each mooring will determine the degree of floatation at each site as the glacier transitions from 365 m to 100 m in thickness. Summer ocean surveys describe the inflowing Atlantic waters that will become diluted by basal melt and by direct injection of freshwater. Thermodynamic constraints on the solid-to-fluid phase transition of glacier ice melted by the ocean result in a characteristic relation of ocean temperatures and salinity (the Gade-line), which is set by the latent heat of melting. A second mixing line arises from ice-shelf surface melting and direct runoff into the fjord. In some fjord systems, this component includes a substantial discharge of subglacial water generated upstream of the grounding line. The proposed temperature-salinity analyses will reveal the importance of this sub-glacial freshwater source along the central melt-channel.

在预测未来全球海平面变化时，大冰川冰盖海洋边缘的冰流失速度是最大的未知数。一系列时间和空间尺度上的许多物理过程决定了这种质量损失，但它们在净损失或增益和趋势中的相对作用却知之甚少。该项目将研究特定系统 Petermann Gletscher (PG) 的冰川-海洋相互作用的物理原理，利用数据来加深对 PG 海洋边缘过程的理解，该过程将格陵兰冰盖 (GIS) 的大部分排入深峡湾通过厚度达 1800 英尺的漂浮冰架与内雷斯海峡相连。在过去的几年里，冰架经历了显着的退缩，从2010年的80公里长到现在的50公里。对内雷斯海峡和彼得曼峡湾深水变暖以及冰架在退缩前十年变薄的观察，得出了一个假设，即基底融化的增加导致了冰架的消失。该项目的动机是 Petermann Gletscher 和 Fjord 系统的三个方面：(1) 它作为 GIS 质量损失门户的重要性； (2) 彼得曼峡湾海洋动力学与先前研究的格陵兰岛南部系统的比较； (3) PG作为一个受良好约束的系统的价值，用于研究导致格陵兰岛北部和南极洲其他冰架系统质量损失的过程及其对全球海平面上升的贡献。该项目利用了该系统的最新观测结果，包括来自冰架下系泊点的持续卫星中继数据。该项目将通过支持培训两名研究生和三名本科生，促进多元化 STEM 劳动力的发展，其中包括一名来自 STEM 领域代表性不足群体的学生。 PI 将继续与瑞典、英国和加拿大合作者开展国际合作，这些合作是 2015 年 I/B Oden 上最初的 Petermann Gletscher 研究的一部分。PI 的网站、博客将促进与公众的接触，偶尔接受媒体采访，并让国家平面媒体记者参与实地工作。时间序列分析将描述冰下水域如何沿着中央融化通道随潮汐和季节变化。 2003 年至 2015 年间船舶在邻近海洋收集的海洋调查数据特性将有助于描述平均状态和解释变化。时域和频域统计分析将揭示相关的时间和空间尺度。更具体地说，傅里叶变换、小波变换和希尔伯特变换将用于提供离散尺度的幅度和相位的估计。频域线性系统分析将揭示代表强迫（例如，海冰移动或不存在时的大气温度和风应力、潮汐）和响应（例如，表面混合层深度、热量）的多个时间序列之间的输入输出关系融水羽流的含量、冰速度和基础融化速率）。当冰川厚度从 365 m 过渡到 100 m 时，对每个系泊处的 GPS 和压力传感器的数据进行分析将确定每个地点的漂浮程度。夏季海洋调查描述了流入的大西洋水域将被基底融化和淡水直接注入稀释。海洋融化的冰川冰从固相到流体相变的热力学约束导致了海洋温度和盐度的特征关系（加德线），这是由融化潜热决定的。第二条混合线是由冰架表面融化和径流直接流入峡湾而产生的。在一些峡湾系统中，该组成部分包括接地线上游产生的大量冰下水的排放。所提出的温度-盐度分析将揭示沿着中央融化通道的冰下淡水源的重要性。