Ice flow dynamics, subglacial hydrology and long-term mass balanceat Lake Vostok from the combination of geodetic GNSS observationsand radio-echo sounding

本提案旨在集中分析、解释和出版南极东部中部沃斯托克冰下湖地区一套独特的大地测量和地球物理现场观测资料。这些数据是申请人及其合作伙伴从2001年至今的9次野外考察中获得的。基于卫星对地表标记物的重复定位，研究冰下湖冰流的速度和方向。该区域的特殊条件限制了遥感技术和冰动力模拟的适用性，使大地测量就地观测成为最可靠的信息来源。将特别注意湖岸上从接地冰到浮冰的过渡，在那里初步观测结果与目前的理论考虑相矛盾。此外，沃斯托克湖地区冰流在气候时间尺度上的变化应受到地表大地测量观测和内部冰层几何形状的综合约束。此外，应结合不同大地测量技术，分离和量化冰下湖局部冰质量平衡、水量变化和水运动对观测高度变化的贡献。地球上最大的冰下湖是测量冰流速度和高度变化的一个特别有希望的目标。这些观测结果可以让我们深入了解冰、冰下水和基岩之间复杂的相互作用，并解释湖泊内部的不同过程。此外，对现在和过去冰流状态的观测约束对于解释Vostok站获取的冰芯至关重要。该项目的结果将结合在Vostok流线的时间积分模型中，该模型确定了特定年龄的岩心冰样的形成位置。这将有助于改进沃斯托克冰芯的多学科解释，这不仅与对沃斯托克湖系统的理解有关，而且与大陆和全球尺度的研究有关。虽然重点是利用现有资料，但实地工作须在整个项目期间继续进行，以确保大地测量监测的连续性。这是在DFG和俄罗斯基础研究基金会（RFBR）之间的谅解备忘录框架内与Sergey V. Popov博士（圣彼得堡PMGE）的合作项目。

This proposal aims at a focused analysis, interpretation and publication of a unique set of geodetic and geophysical in-situobservations in the region of subglacial Lake Vostok, central East Antarctica. These data have been obtained by the applicant and his cooperation partner during nine field expeditions since 2001 up to now. Based on repeated satellite positioning on surface markers the velocity and direction of ice flow across the subglacial lake shall be investigated. The particular conditions in this region limit the applicability of remote sensing techniques and ice-dynamic modelling and make geodetic insitu observations the most reliable source of information. Special attention will be paid to the transition from grounded to floating ice across the lake's shore where preliminary observational results contradict current theoretical considerations. Furthermore, the variability of ice flow in the Lake Vostok region over climatic timescales shall be constrained by a combination of geodetic observations at the surface with the geometry of internal ice layers. In addition, different geodetic techniques shall be combined to separate and quantify the contributions of local ice-mass balance, water volume changes and water movements within the subglacial lake to observable height changes. The largest subglacial lake on Earth represents a particularly promising target for the geodetic determination of ice-flow velocities and height changes. These observations allow insights into the complex interactions between ice, subglacial water and bedrock and interpretations regarding different processes within the lake. Moreover, observational constraints on thepresent and past ice-flow regime are crucial for the interpretation of the ice core retrieved at Vostok station. The results of this project shall be combined in a time-integrating model for the Vostok flowline that determines where ice samples of the core of a certain age were formed. This will contribute to the improvement of the multidisciplinary interpretation of the Vostok ice core that is relevant not only for the understanding of the Lake Vostok system, but also for research on continental and global scales. Although the emphasis is given on the utilization of existing data, the fieldwork shall be continued throughout the project duration to ensure the continuity of the geodetic monitoring. This is a cooperation project with Dr. Sergey V. Popov (PMGE, St. Petersburg) in the frame of the MoU between DFG and the Russian Foundation of Basic Research (RFBR).