北冰洋西部过去130ka海冰演变记录及其对碳循环的影响

Sea ice is a fundamental component of Earth’s climate system, significantly influencing the global climate as well as the climate and extreme weather in China. As the global temperature has been increasing since the last decades, the Arctic summer sea ice cover is declining rapidly, with an intensification of ocean acidification as a carbon sink. However, the lack of quantitative reconstruction of long-term sea-ice variability and organic carbon contribution hinders the understanding of Arctic and global warming and its influence on carbon cycle. The sea-ice declining in the western Arctic is much rapider than that in other Arctic regions, sensitive to the climate change. Furthermore, the burial and preservation rates of organic carbon in this area is high, which records the climate change well. We will use the historical records of biomarkers (IP25, sterols and n-alkanols) and bulk index (TOC, δ13C and Δ14C) for the past 130 ka in continuous sediment cores (with age control) taken from the western Arctic, to quantitatively reconstruct the temporal sea ice variability and reveal the history of sea ice evolution, to quantitatively estimate the contribution of different sources of organic carbon and explain the influence of sea ice variation on organic carbon sources and the relationship between the sea ice variability and organic carbon input. By comparing the previous studies and records between MIS 5 warm period without anthropogenic influence and today, this study will reveal the response mechanism of climate change to natural drive. The research results are of great significance to understand the mechanism of Arctic rapid climate change and global warming and will provide important reference for predicting the future climate change.

海冰是全球气候系统的重要组成部分，其变化对全球气候及我国气候和极端天气有显著影响。近几十年全球日益变暖，北极夏季海冰覆盖面积急剧下降、碳汇增加且海洋酸化加剧，但目前缺乏对北极海冰和沉积有机碳长时间尺度的定量研究，限制了对北极和全球变暖机制及其对碳循环影响的深入认识。北冰洋西部的海冰消退面积远高于其它区域，对气候变化敏感；且该海域沉积有机碳埋藏效率高，较好地记录了气候变迁。我们拟选取具有年代框架的北冰洋西部连续沉积物岩芯，建立生物标志物（IP25、甾醇、烷醇）和总有机质（TOC、δ13C、Δ14C）过去130ka的沉积记录，定量重建海冰密集度，揭示海冰演化历史；定量估算有机碳贡献，阐明海冰变化对有机碳来源的影响；通过无人类活动影响的MIS5暖期与现代资料和近代记录的对比，揭示气候变化对自然驱动的响应。研究成果对了解现代北极气候快速变化和全球变暖机制有重要启示，为预测未来气候变化提供参考依据。

海冰是地球系统的重要组成部分，对全球的温盐环流和气候变化有重要作用。近几十年来北极气候快速变化、夏季海冰覆盖面积急剧减小，但是目前北极海冰快速减少的机制尚不明确。西北冰洋是连接北冰洋和太平洋的重要区域，该区域季节性海冰覆盖程度高且季节间海冰边缘迁移距离较远。在近10年来北冰洋海冰快速下降的情形下，西北冰洋及其边缘区域的海冰消退面积要远远高于北冰洋其它边缘海，对气候变化十分敏感。此研究的科学问题首先是北冰洋西部海冰演化历史，其次是海冰变化对有机碳来源的影响过程。本项目聚焦西北冰洋的楚科奇海，广泛搜集有关北冰洋海域及亚北极区域的古气候、古海冰资料，以及现代卫星观测海冰数据，用于对比分析北冰洋不同扇区海冰和气候异同；通过测定表层沉积物和沉积物岩芯的总有机质参数（TOC及其碳同位素）以及不同来源的生物标志物（海冰生物标志物、浮游植物生物标志物和陆源生物标志物），校正了泛北极沉积物中的海冰指标和卫星观测海冰密集度的相关性；重建了过去百年以及冰期-间冰期海冰变化及其对碳循环的影响，对认识当前北极快速变化对全球变暖的驱动有重要意义，而且能为预测未来气候变化提供依据。