Crustal uplift rates of 4 GPS stations near Jakobshavn Isbrae (2006-2009)

We analyze 2006-2009 data from four continuous Global Positioning System (GPS) receivers located between 5 and 150 km from the glacier Jakobshavn Isbrae, West Greenland. The GPS stations were established on bedrock to determine the vertical crustal motion due to the unloading of ice from Jakobshavn Isbrae. All stations experienced uplift, but the uplift rate at Kangia North, only 5 km from the glacier front, was about 10 mm/yr larger than the rate at Ilulissat, located only ~45 km further away. This suggests that most of the uplift is due to the unloading of the Earth's surface as Jakobshavn thins and loses mass. Our estimate of Jakobshavn's contribution to uplift rates at Kangia North and Ilulissat are 14.6 ± 1.7 mm/yr and 4.9 ± 1.1 mm/yr, respectively. The observed rates are consistent with a glacier thinning model based on repeat altimeter surveys from NASA's Airborne Topographic Mapper (ATM), which shows that Jakobshavn lost mass at an average rate of 22 ± 2 km**3/yr between 2006 and 2009. At Kangia North and Ilulissat, the predicted uplift rates computed using thinning estimates from the ATM laser altimetry are 12.1 ± 0.9 mm/yr and 3.2 ± 0.3 mm/yr, respectively. The observed rates are slightly larger than the predicted rates. The fact that the GPS uplift rates are much larger closer to Jakobshavn than further away, and are consistent with rates inferred using the ATM-based glacier thinning model, shows that GPS measurements of crustal motion are a potentially useful method for assessing ice-mass change models.

我们分析了2006至2009年间，取自西格陵兰雅各布港冰川（Jakobshavn Isbrae）5至150公里范围内的四台连续运行的全球定位系统 (Global Positioning System) 接收机的数据。这些测站均设置于基岩之上，旨在探究由雅各布港冰川冰量卸载引发的地壳垂直运动。所有测站均观测到地壳抬升，但距冰川前缘仅5公里的康加北（Kangia North）测站的抬升速率，比仅远约45公里的伊卢利萨特（Ilulissat）测站高出约10毫米/年。这表明绝大多数抬升现象源于雅各布港冰川变薄、冰量流失所引发的地表卸载效应。我们估算得出，雅各布港冰川对康加北和伊卢利萨特两处测站抬升速率的贡献分别为14.6±1.7毫米/年与4.9±1.1毫米/年。观测到的抬升速率与基于美国国家航空航天局 (National Aeronautics and Space Administration，NASA) 机载地形测绘仪 (Airborne Topographic Mapper，ATM) 重复测高调查所得的冰川变薄模型相符，该模型显示2006至2009年间雅各布港冰川的平均冰量流失速率为22±2立方千米/年。基于该ATM激光测厚数据估算得到的冰川变薄量，计算得出康加北与伊卢利萨特两处的理论抬升速率分别为12.1±0.9毫米/年与3.2±0.3毫米/年。实际观测到的抬升速率略高于理论预测值。GPS抬升速率随距雅各布港冰川距离越近而越高，且与基于ATM的冰川变薄模型推导所得速率相一致，这一事实表明，地壳运动的GPS测量手段可作为评估冰量变化模型的潜在有效方法。