The Antarctic Ice Sheet influences the global temperature and sea level by complex interactions with the atmosphere and the ocean and is thus an important factor in the Earth's climate system. Recent climate assessments reveal a steady increase of global temperatures and an on-going shrinking of glaciers and ice sheets. Because the total Antarctic ice volume has the potential to raise the global sea level by about 58 meters, it is of particular interest to understand the ice dynamics regarding the mass export and thus the contribution to sea level rise. Observations of the last decades reveal a widespread hydrological system of subglacial lakes and drainage networks beneath the Antarctic Ice Sheet which is recognized to have a large impact on the ice dynamics. The aim of this thesis is to investigate this subglacial hydrological environment and its interactions with the ice flow dynamics of the overlying ice sheet.ududFor reaching this aim, the ice flow model RIMBAY is enhanced by a subglacial hydrology module which provides the simulation of basal water flow and the identification of positions and extents of subglacial lakes. This model is then applied to the Antarctic Ice Sheet. A subsequent validation by the analysis of ice-penetrating radar profiles in Dronning Maud Land leads to the identification of 31 new potential subglacial lake locations. Based on these findings, the total number of Antarctic subglacial lakes is estimated to be 1300±300, a factor of three more than what has been discovered so far. Their overall extent is assessed to cover about 0.6% of the Antarctic ice-bed interface. Furthermore, strong correlations are found between modeled pathways of basal water flow and observed locations of ice streams.ududIn a detailed investigation of the Ross Ice Streams at the Antarctic Siple Coast the local basal driver of fast ice flow is identified as water saturated and unconsolidated sediment. The assessment of the basal flow regime enables the simulation of basal drainage patterns which are clearly associated with current patterns of fast ice flow. The application of satellite-observed ice surface elevation changes to the present-day ice sheet geometry additionally allows prognostic water flow simulations. They reveal a high dynamic of basal water pathways. In particular, a major hydraulic tributary of the Kamb and Whillans Ice Stream is redirected towards the Bindschadler Ice Stream within the next 200 years, possibly resulting in future increase of ice velocities within the Bindschadler Ice Stream.ududIn order to gain further insights into the complex feedback mechanisms between an ice sheet and its subglacial environment, ice dynamics and subglacial hydrology are modeled in a coupled approach for a synthetic domain. A new hydrological concept is developed and implemented in RIMBAY, providing the dynamic generation of subglacial lakes and covering the spatial and temporal variability of basal drainage systems. The impact of basal hydrology on the ice dynamic is estimated in various experiments, considering distinct feedback mechanisms. It is demonstrated, that a coupling at full complexity leads to a considerably negative mass balance of the investigated synthetic ice sheet. The results reveal the capabilities of the new hydrological concept and emphasize the necessity to incorporate subglacial hydrology in ice sheet models.
展开▼
机译：南极冰盖通过与大气和海洋的复杂相互作用影响全球温度和海平面，因此是地球气候系统的重要因素。最近的气候评估显示，全球温度稳定上升，冰川和冰盖不断缩小。由于南极的总冰量有可能使全球海平面上升约58米，因此特别需要了解有关大量出口的冰动力学，从而对海平面上升做出贡献。过去几十年的观测结果表明，南极冰盖下方的冰湖湖泊和排水网络具有广泛的水文系统，这被认为对冰动力学具有重大影响。本文的目的是研究这种冰川下的水文环境及其与上覆冰原冰流动力学的相互作用。 ud ud为了实现这一目标，通过冰川下的水文模块增强了冰流模型RIMBAY，该模块提供了模拟底水流的变化及冰下湖泊的位置和范围的确定。然后将此模型应用于南极冰盖。通过对Dronning Maud Land的穿透冰雷达剖面的分析，随后进行的验证导致确定了31个新的潜在冰河湖潜在位置。根据这些发现，南极冰河下湖泊的总数估计为1300±300，是迄今为止发现的三倍。据评估，它们的总体覆盖范围约为南极冰床界面的0.6％。此外，在基础水流的模拟路径与冰流的观测位置之间发现了很强的相关性。 ud ud在对南极Siple海岸的Ross冰流进行的详细调查中，快速冰流的本地基础驱动力被确定为水饱和和未固结的沉积物。对基础流态的评估使得能够模拟与当前快速冰流模式明显相关的基础排水模式。将卫星观测的冰面高度变化应用于当今的冰盖几何形状还可以进行预后水流模拟。它们揭示了基础水通道的高度动态。特别是，Kamb和Whillans冰河的主要水力支流在接下来的200年内将重新定向到Bindschadler冰河，这可能导致Bindschadler冰河内的冰速未来增加。 ud ud为了获得更多见解。在冰盖及其冰下环境之间复杂的反馈机制中，冰动力和冰下水文学以合成方法的耦合方法建模。在RIMBAY中开发并实施了一种新的水文概念，提供了冰河下湖泊的动态生成，并涵盖了基础排水系统的时空变化。考虑到不同的反馈机制，在各种实验中估算了基础水文学对冰动力学的影响。已经证明，完全复杂的耦合导致所研究的合成冰盖的相当大的负质量平衡。结果揭示了新的水文概念的功能，并强调了将冰下水文学纳入冰盖模型的必要性。
展开▼
