Assessment of Basal Melt of Petermann Gletscher in Northwestern Greenland

格陵兰岛西北部 Petermann Gletscher 基底融化的评估

• 批准号: 0135450
• 负责人: Konrad Steffen
• 金额: $ 18.2万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-01 至 2006-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0135450&HistoricalAwards=false
• 关键词: Assessment; Basal; Melt; Petermann; Gletscher

0135450SteffanThe research is a collaborative effort between the University of Colorado, Boulder, the British Antarctic Survey, Cambridge, and the Jet Propulsion Laboratory. The Office of Polar Programs (OPP) at National Science Foundation and the National Aeronautical and Space Administration (NASA) will support the project. The Greenland Ice Sheet is thinning rapidly along its outlet glaciers and is contributing an estimated 0.13 mm/yr global sea level rise. Signs of its warming have been documented, including rising air temperature in its central part and retreating sea ice in its surrounding ocean. Extensive floating ice tongues in the northwest sector are ice undergoing massive rates of ablation from the surrounding warm ocean waters and are presently in a state of fragile equilibrium, but this ablation rate has never been measured. The Petermann Gletscher is the largest and most influential outlet glacier in northern Greenland, draining an area of 71,580 km2, with a discharge of 12 cubic km of ice per year. Remote sensing results suggest that its ice discharge exceeds that required to maintain the ice sheet interior in a state of mass equilibrium by 63%, and its grounding line is retreating at an anticipated rate at nearly one meter per year. Its floating ice tongue is only a few meters above sea level at the ice front, so it is highly vulnerable to ice thinning. If confirmed by in-situ observations and if this trend continues for several decades, the rate of thinning would be sufficient to threaten the stability and survival of the ice tongue. The Principal Investigators propose to do a detailed analysis of the glacier floating ice tongue in front of Petermann Gletscher that integrates key field observations with remote sensing data. The field program is designed to obtain the in-situ observations to confirm, validate, and calibrate the remote sensing estimates of basal melting, derive reliable estimates of surface melt from an energy balance model, observe changes in ice volume with precision, and understand the contribution of ice dynamics, surface melt and bottom melt to volume changes of floating ice. The experiment is will take place at the most crucial part of the glacier, the grounding line. Bottom melt rates are estimated to reach 25 m/yr near the grounding zone from remote sensing data, and 75% of the ice that crosses melts in contact with warm ocean waters in the first 20% area of floating ice. Basal melting will be measured in-situ over several time intervals using a novel phase-sensitive radar sounding system developed and tested by the British Antarctic Survey. At the surface, the energy budget of the ice will be characterized using a network of automated micrometeorological stations, and the results will be employed to determine how well surface melt can be predicted from an energy balance model and how much it changes with time. Remote sensing data that include strain rates from interferometric synthetic-aperture radar (InSAR), elevation changes from airborne laser altimetry, and ice thickness from airborne ice-radar sounding, will be employed to yield spatial estimates of basal melting to be compared with in-situ data. InSAR and Global Positioning Systems will be used to detect changes in flow rate with time. The results will provide invaluable insights into dynamics and climatic processes of northern Greenland glaciers.

0135450斯蒂芬这项研究是博尔德的科罗拉多大学、剑桥的英国南极调查局和喷气推进实验室之间的合作成果。 美国国家科学基金会极地项目办公室（Office of Polar Programs）和美国国家航空航天局（NASA）将支持该项目。 格陵兰冰盖正沿着其出口冰川沿着迅速变薄，估计每年造成全球海平面上升0.13毫米。它变暖的迹象已经被记录在案，包括其中部气温上升和周围海洋海冰退缩。在西北地区的大量浮冰舌是从周围温暖的海洋沃茨中大量消融的冰，目前处于脆弱的平衡状态，但这种消融率从未被测量过。Petermann Gletscher是格陵兰北方最大和最有影响力的出口冰川，排水面积为71，580平方公里，每年排放12立方公里的冰。 遥感结果表明，它的冰流量超过了维持冰盖内部质量平衡所需的63%，其接地线正在以每年近一米的速度后退。它的浮冰舌在冰锋处仅高出海平面几米，因此它非常容易受到冰变薄的影响。如果得到现场观测的证实，并且这种趋势持续几十年，那么变薄的速度将足以威胁冰舌的稳定和生存。 主要研究人员建议对彼得曼·格莱切尔前面的冰川浮冰舌进行详细分析，将关键的实地观测与遥感数据相结合。现场方案的目的是获得现场观测，以确认，验证和校准遥感估计的基底融化，从能量平衡模型获得可靠的估计表面融化，观察冰量的变化与精度，并了解冰动力学，表面融化和底部融化的浮冰体积变化的贡献。实验将在冰川最关键的部分--接地线上进行。根据遥感数据，底部融化速率估计在接地区附近达到25米/年，在前20%的浮冰区，75%的穿越融化的冰与温暖的海洋沃茨接触。将使用英国南极调查局开发和测试的一种新的相敏雷达探测系统，在若干时间间隔内对基底融化进行现场测量。在地表，将使用自动微气象站网络来表征冰的能量收支，并将利用结果来确定从能量平衡模型预测地表融化的程度以及它随时间的变化程度。将利用遥感数据，包括干涉合成孔径雷达（干涉合成孔径雷达）的应变率、机载激光测高的海拔变化和机载冰雷达探测的冰厚，对基底融化进行空间估计，并与现场数据进行比较。将使用干涉合成孔径雷达和全球定位系统探测流速随时间的变化。研究结果将为了解北方格陵兰冰川的动态和气候过程提供宝贵的见解。