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

南极西部冰盖造成了南极冰质量损失的最大份额，据估计，南极冰质量损失平均约为150亿吨/年，相当于全球海平面上升约为0.4毫米/年。在21世纪，这种海洋冰盖的崩塌可能会使全球海平面远远高于预测范围。除了南极半岛北部，阿蒙森海是最敏感的变化区域。特别是由松树岛冰川、思韦茨冰川和史密斯冰川的主要冰流组成的阿蒙森海海湾，造成了主要的质量损失。因此，在过去的几年里，该地区已发展成为一个热点地区的兴趣，加强调查。为了确定冰-质量平衡，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，以及精确的、重复的原位GPS测量。然而，不确定性的主要来源，也就是迄今为止卫星重力估算冰-质量平衡的最大误差成分，仍然来自冰川均衡平差（GIA）校正。这种影响与现今冰质量变化本身在同一数量级上。除了复杂的模型外，南极GIA预测仍然缺乏观测约束和冰载历史和地球流变学的足够复杂性。因此，我们将从整个大陆的考虑开始，然后将我们的调查重点放在阿蒙森海地区，这是显示出最大的冰量损失和变化的地区之一。首先，我们将利用卫星重力测量和卫星高度测量相结合的方法来估算GIA效应。这一估计将通过独立的、基于地面gps的垂直变形数据进行验证。为此，将在调查区域进行重复的GPS测量，主要是在德国R/V北极星号的ANT-XXX/3巡航期间。其次，大地GIA估计将用作精细GIA建模的约束。该区域模型的改进将基于最新的全南极洲GIA模型IJ05-R2 (Ivins et al., 2013)，并允许研究地球流变学和冰负荷历史的变化。为了改进区域GIA模型，还应考虑地球物理学、冰川形态和地质学的研究结果，这尤其有助于更好地约束冰荷载变化的时间和位置。区域改进的GIA模型将被整合到优越的全南极洲GIA模型中，用于迭代地获得更好的冰-质量平衡和对全球海平面变化的等效贡献的估计，并进行全面的误差评估。

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.