Sedimentary Records of the Evolution of the Melville Bugt Ice Stream

作为对持续气候强迫的响应，格陵兰冰盖（GrIS）在范围和质量平衡方面发生了变化，对北大西洋的海平面和海洋学产生了影响。考虑到GrIS有可能使全球海平面上升约7米，而超过1.5亿人生活在距离当前海平面仅1米的地方，了解冰盖的长期历史具有全球社会意义。充分了解过去GrIS对气候变化的动态响应是模拟和预测未来情景的关键。关于末次极大期（LGM）和新仙女木期（Younger Dryas GrIS）的范围和退缩动力学的研究数据越来越多，但这些数据严重偏向于西格陵兰岛Disko Bugt的Jakobshavn Isbræ。在这个区域之外，人们对冰川消融的时间和动力学的了解还不太充分。例如，位于Disko Bugt西北的Melville Bugt海槽（MBT）的海底直到最近才被绘制出来，并显示冰到达了LGM的大陆架边缘，使其比以前认为的要超前约80公里（Newton et al., 2017）。如果MBT完全被LGM的冰流所占据，正如海底地形所暗示的那样，它将会排干GrIS的面积至少是Jakobshavn Isbræ（目前排干GrIS的7%）的三倍，这突出了更好地了解其后LGM演变的必要性。该项目旨在通过对MBT沉积物的分析，揭示过去推动冰盖退缩的机制和过程，以及这些过程是线性的、稳定的还是非线性的、灾难性的。研究区域靠近最近在格陵兰岛西北部发现的流星撞击地点，这意味着在近海沉积记录中也可能保存了补充证据（例如震荡石英），这可能有助于解开新仙女木期的原因。对岩石变化和有孔虫组合的演化进行分析，将有助于了解西格陵兰洋流的演化及其与该地区冰盖动力学的关系。为了解决这些问题，我们将使用一系列沉积学、古生物学、地球化学和统计技术，对从梅尔维尔堡研究区提取的六个浅层沉积物岩心进行分析。这些分析的结果将为重建格陵兰岛这一地区的古海洋学和环境变化提供机会，从而更全面地了解过去冰盖演变的情况，以及这对气候变暖下未来情景的潜在影响。

In response to ongoing climate forcing the Greenland Ice Sheet (GrIS) has experienced changes in extent and mass balance, with implications for sea level and oceanography of the North Atlantic. Given that the GrIS has the potential to add up to ~7 m to global sea-level, and that over ~150 million people live within just 1 m of current sea-level, understanding the long-term history of the ice sheet is of global societal significance. A full understanding of past GrIS dynamics in response to climate change is key to modelling and projecting future scenarios. There is an increasing volume of data from studies of the Last Glacial Maximum (LGM) and Younger Dryas GrIS extent and retreat dynamics, but these data are heavily skewed towards Jakobshavn Isbræ in Disko Bugt, West Greenland. Outside this region there is a less well developed understanding of the timing and dynamics of deglaciation. For example, the seafloor of the Melville Bugt Trough (MBT) to the northwest of Disko Bugt has only recently been mapped and shows that ice reached the shelf edge at the LGM, making it ~80 km more advanced than previously thought (Newton et al., 2017). If the MBT was fully-occupied by an ice stream at the LGM, as suggested by seafloor landforms, it would have drained an area of the GrIS at least three times larger than Jakobshavn Isbræ (which currently drains ~7% of the GrIS), highlighting the need for a better understanding of its post-LGM evolution. This project aims to unravel the mechanisms and processes that drove ice sheet retreat in the past, and whether these processes were linear and steady or non-linear and catastrophic, through the analysis of sediments in MBT. The proximity of the study area to the recently identified meteor impact site in northwest Greenland means that complimentary evidence may also be preserved in the offshore sedimentary record (e.g. shocked quartz) and may help unravel the causes of the Younger Dryas. Analysis of lithological changes and the evolution of foraminifera assemblages will provide insights into the evolution of the West Greenland Current and its relationship with ice sheet dynamics in the region. To address these ideas six shallow sediment cores, retrieved from the study area in Melville Bugt, will be analysed using a range of sedimentological, palaeontological, geochemical, and statistical techniques. The results of these analyses will offer the opportunity to reconstruct palaeoceanography and environmental changes in this area of Greenland to develop a more complete picture of ice sheet evolution in the past and the potential implications this has for future scenarios under a warming climate.