Seasonal velocities of eight major marine-terminating outlet glaciers of the Greenland ice sheet from continuous in situ GPS instruments

We present 17 velocity records derived from in situ stand-alone single-frequency Global Positioning System (GPS) receivers placed on eight marine-terminating ice sheet outlet glaciers in South, West and North Greenland, covering varying parts of the period summer 2009 to summer 2012. Common to all the observed glacier velocity records is a pronounced seasonal variation, with an early melt season maximum. The GPS-derived velocities are compared to velocities derived from radar satellite imagery over six of the glaciers to illustrate the potential of the GPS data for validation purposes. Three different velocity map products are evaluated, based on ALOS/PALSAR data, TerraSAR-X/Tandem-X data and an aggregate winter TerraSAR-X data set. The velocity maps derived from TerraSAR-X/Tandem-X data have a mean difference of 1.5% compared to the mean GPS velocity over the corresponding period, while velocity maps derived from ALOS/PALSAR data have a mean difference of 8.3%. The velocity maps derived from the aggregate winter TerraSAR-X data set have a mean difference of 9.5% to the corresponding GPS velocities.

本研究构建了17条冰川流速记录，数据来自部署于格陵兰南部、西部及北部8条入海冰盖出口冰川上的原位独立单频全球定位系统（Global Positioning System，GPS）接收机，观测时段覆盖2009年夏季至2012年夏季的不同区间。所有观测得到的冰川流速记录均存在显著的季节性变化，且在融冰季早期达到流速峰值。为阐明GPS数据用于冰川流速验证的潜力，本研究将GPS反演得到的流速与其中6条冰川的雷达卫星影像反演流速进行了对比。本研究评估了三种不同的流速图产品，其数据源分别为ALOS/PALSAR数据、TerraSAR-X/Tandem-X数据以及冬季合成TerraSAR-X数据集。基于TerraSAR-X/Tandem-X数据生成的流速图，与对应时段的GPS平均流速相比，平均偏差为1.5%；基于ALOS/PALSAR数据生成的流速图平均偏差为8.3%；而基于冬季合成TerraSAR-X数据集生成的流速图，与对应GPS流速的平均偏差为9.5%。