全新世极地海洋环境与格陵兰南部冰盖消长关系探讨

The Greenland Ice Sheet is the largest ice body in the Northern Hemisphere. In recent years accelerated melt of the Greenland Ice Sheet has caused great concern as to its response and the associated sea level rise as climate continues to warm in the future. However, the causes of recent glaciological changes are still unclear for the lack of the instrumental/satellite data. This underlines the importance of quantitative reconstructions of glacier activity of the Greenland Ice Sheet as well as the surrounding oceanographic background, and systematical studies on the linkage between them in the long time scales..The purpose of this project is thus three-fold: 1) To reconstruct high-resolution sea-surface temperature and sea-ice records during the Holocene based on diatom transfer function and other proxy records. 2) To reconstruct glaciological changes of the southern Greenland Ice Sheet during the Holocene using the variability in iceberg rafted debris. 3) To assess the behavior of the ice margin in response to varying oceanic and climatic conditions using these quantitative reconstructed records. Finally, with aid of numerical modelling, the interacting mechanism between the glacier activity and ocean conditions will be further investigated to provide an in-depth understanding of role played by ocean-cryosphere system on climate evolution since the Holocene.

格陵兰冰盖—北半球现存的唯一大陆冰盖，近几十年来正处于快速消融阶段。然而受限于卫星遥感数据的缺失，其加速消融的主要原因仍存在较多争议。因此，定量重建长时间尺度的极地海洋环境与格陵兰冰盖演化，查明其相互关系，不仅可以找出影响格陵兰冰盖消长的主要驱动因素，而且对预测未来格陵兰冰盖演化趋势具有重要意义。.本项目以格陵兰南部三个最主要的冰盖消融区为研究区域，首先根据硅藻转换函数、有孔虫氧碳同位素等指标，定量重建格陵兰南部全新世海洋环境演变；然后通过沉积物粒度及冰筏碎屑含量分析，定量重建全新世以来格陵兰南部冰盖演化记录；最后运用频谱分析、小波分析、滑动相关分析及交叉相关分析等方法，分析全新世以来格陵兰南部冰盖演化与北大西洋暖水团/极地冷水团的强弱变化、极地海冰变化等的相关性，试图找到影响格陵兰冰盖消长的主要驱动因素，并通过COSMOS模式，模拟不同海洋环境要素对格陵兰冰盖演化的影响权重及其影响机制。

项目组首先运用微体古生物、生物地球化学等多种指标，并结合转换函数方法，定量重建了格陵兰南部海域全新世以来的海水表层温度、海冰覆盖度等海洋环境要素；然后通过分析不同粒级的冰筏碎屑含量变化及分布，并结合格陵兰冰芯记录，重建了全新世以来格陵兰南部冰盖的演化历史；最后运用多种数理统计方法，分析了全新世以来格陵兰南部海域海洋环境变化与格陵兰冰盖演化的相关关系及内在联系。早全新世期间，较高的太阳辐射使得海水表层温度较高海冰覆盖极低，而温盐环流和副极地环流的减弱，使得印明格暖流不断增强，进而导致格陵兰南部冰盖大量消融。全新世大暖期时，格陵兰南部冰盖因前期的大量消融而达到最低值。中全新世期间，东格陵兰寒流携带的极地冷水团显著增强，而印明格暖流携带的大西洋暖水的影响开始减弱，进而导致冰山携带碎屑物质增加，冰筏碎屑含量较高。而晚全新世以来，随着东格陵兰寒流的进一步增强海冰覆盖显著增加，反而导致冰山携带的碎屑物质难以到达研究区。