Investigating Ice-Mass Balance and Glacial Isostatic Adjustment in the Amundsen Sea Sector, West Antarctica, by Geodetic Observations and Modelling

西南极冰盖是造成南极冰量损失最大的部分，估计平均约为1.5亿吨/年，相当于全球海平面上升约0.4毫米/年。这片海洋冰盖的崩溃可能会使全球海平面在21世纪远高于预测的范围。除了南极北方半岛外，阿蒙森海部分是变化最敏感的区域。特别是，阿蒙森海湾，包括松岛冰川，思韦茨冰川和史密斯冰川的主要冰流，占质量损失的主要部分。因此，在过去的几年里，该地区已发展成为一个热点地区的利益，加强调查。为了确定冰量平衡，拟议的项目利用卫星重力测量和卫星测高的大地测量技术以及精确、重复的现场全球定位系统测量。然而，不确定性的主要来源，因此，到目前为止，最大的误差成分，在卫星重力估计的冰质量平衡仍然来自冰川均衡调整（GIA）的校正。这种影响与现今冰量变化本身处于同一数量级。除了复杂的建模外，南极GIA预测仍然缺乏观测约束，冰负荷历史和地球流变学也缺乏足够的复杂性。因此，我们将从整个大陆的考虑出发，然后将我们的调查重点放在阿蒙森海区，这是冰量损失和变化最大的地区之一。我们将利用，首先，卫星重力测量和卫星测高相结合，提出一个GIA效应的估计。这一估计将由独立的地面GPS垂直变形数据进行验证。为此，将主要在德国“Polarstern”号研究船ANT-XXX/3号巡航期间，在调查区域进行重复的全球定位系统测量。其次，大地GIA估计将被用作一个完善的GIA模型的约束。该区域模型改进将基于最新的全舌GIA模型IJ 05-R2（Ivins等人，2013年），并允许研究地球流变学和冰荷载历史的变化。对于改进的区域GIA建模，还应考虑到地球物理学、冰川形态学和地质学的调查结果，这尤其有助于更好地限制变化的冰负荷的时间和位置。区域改进的GIA模型-纳入上级舌宽GIA模型-将被用来迭代获得更好的估计冰质量平衡和等效的全球海平面变化的贡献，以及整个误差评估。

The West Antarctic Ice Sheet is responsible for the largest share of the Antarctic ice-mass loss, which is estimated to be on average in the order of 150 Gt/yr, the equivalent global sea-level rise of which would amount to about 0.4 mm/yr. A collapse of this marine-based ice sheet could raise global sea level far above predicted ranges during the 21st century. Besides the northern Antarctic Peninsula, the Amundsen Sea sector is the most sensitive region of change. In particular, the Amundsen Sea embayment, comprising the major ice streams of Pine Island Glacier, Thwaites Glacier and Smith Glacier, accounts for the major part of the mass loss. Hence, over the past years this region has developed into a hot spot area of interest for intensified investigation. To determine the ice-mass balance the proposed project utilizes the geodetic techniques of satellite gravimetry and satellite altimetry together with precise, repeated in-situ GPS measurements. However, the main source of uncertainty and, thus, by far the largest error component in satellite-gravimetric estimates of the ice-mass balance still originates from the glacial-isostatic adjustment (GIA) correction. This effect is in the same order of magnitude as the present-day ice-mass change itself. Besides their sophisticated modelling Antarctic GIA predictions still lack observational constraints and a sufficient complexity both of the ice-load history and of the Earth rheology. Therefore, we will start from a continent-wide consideration and will then focus our investigations on the Amundsen Sea sector, one of those regions showing the largest ice-mass loss and variability. We will utilize, firstly, a combination of satellite gravimetry and satellite altimetry to come up with an estimation of the GIA effect. This estimation will be validated by independent, ground-based GPS-derived vertical deformation data. For this, repeated GPS measurements will be carried out in the area of investigation, mainly during the cruise ANT-XXX/3 of the German R/V Polarstern. Secondly, the geodetic GIA estimates will be used as constraints for a refined GIA modelling. This regional model refinement will be based on the latest Antarctic-wide GIA model IJ05-R2 (Ivins et al., 2013) and allows to study variations in Earth rheology and ice-load history. For an improved regional GIA modelling also the results of investigations in geophysics, glacial morphology and geology shall be taken into consideration, which can especially help to better constrain the timing and position of the changing ice load. The regionally improved GIA model - incorporated into the superior Antarctic-wide GIA model - will be utilized to iteratively gain a better estimate of the ice-mass balance and the equivalent contribution to global sea-level change together with a throughout error assessment.