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

西南极冰盖是南极冰块损失的最大部分，估计平均约为150GT/年，相当于全球海平面上升约0.4毫米/年。这种以海洋为基础的冰盖的崩溃可能会使全球海平面在21世纪远远超过预测的范围。除了南极半岛北部，阿蒙森海区是变化最敏感的地区。尤其是阿蒙森海湾，包括松岛冰川、斯韦茨冰川和史密斯冰川的主要冰流，是造成质量损失的主要原因。因此，在过去的几年里，该地区已发展成为加强调查的热点地区。为了确定冰块平衡，拟议的项目利用了卫星重力测量和卫星测高的大地测量技术，以及精确的、重复的现场GPS测量。然而，冰块平衡卫星重力估算的主要不确定因素，也是迄今为止误差最大的部分，仍然来自冰川均衡调整(GIA)校正。这种影响与今天的冰块变化本身具有相同的量级。除了其复杂的模型外，南极GIA预测仍然缺乏观测限制和足够的冰负荷历史和地球流变学的复杂性。因此，我们将从整个大陆的考虑开始，然后将重点放在阿蒙森海区，这是冰块质量损失和可变性最大的区域之一。首先，我们将利用卫星重力测量和卫星测高相结合的方法来估计GIA效应。这一估计将得到独立的、基于地面的GPS垂直形变数据的验证。为此，将在调查区域进行重复的GPS测量，主要是在德国R/V Polarstein号巡航ANT-XXX/3期间。其次，大地测量GIA估计将被用作改进GIA建模的约束。这一区域模型的改进将以最新的南极GIA模型IJ05-R2(依文斯等人，2013年)为基础，并允许研究地球流变学和冰载历史的变化。对于改进的区域GIA模型，还应考虑到地球物理、冰川形态和地质学的调查结果，这尤其有助于更好地限制冰负荷变化的时间和位置。区域改进的GIA模型--合并到优越的南极范围GIA模型--将被用来迭代地获得对冰块平衡和对全球海平面变化的同等贡献的更好估计，以及全面误差评估。

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.