High-resolution IP25 of three sediment cores in the western North Pacific and Bering Sea@en

Due to its strong influence on heat and moisture exchange between the ocean and the atmosphere, sea ice is an essential component of the global climate system. In the context of its alarming decrease in terms of concentration, thickness and duration, understanding the processes controlling sea-ice variability and reconstructing paleo-sea-ice extent in polar regions have become of great interest for the scientific community. In this study, for the first time, IP25, a recently developed biomarker sea-ice proxy, was used for a high-resolution reconstruction of the sea-ice extent and its variability in the western North Pacific and western Bering Sea during the past 18,000 years. To identify mechanisms controlling the sea-ice variability, IP25 data were associated with published sea-surface temperature as well as diatom and biogenic opal data. The results indicate that a seasonal sea-ice cover existed during cold periods (Heinrich Stadial 1 and Younger Dryas), whereas during warmer intervals (Bølling-Allerød and Holocene) reduced sea ice or ice-free conditions prevailed in the study area. The variability in sea-ice extent seems to be linked to climate anomalies and sea-level changes controlling the oceanographic circulation between the subarctic Pacific and the Bering Sea, especially the Alaskan Stream injection though the Aleutian passes.海冰对海洋与大气间的热量和水汽交换具有显著调控作用，是全球气候系统的核心组成部分。当前海冰的覆盖率、厚度及存续时长均呈现令人担忧的下降趋势，在此背景下，解析海冰变化的控制机制并重建极地古海冰分布范围，已成为国际科学界的重点研究方向。本研究首次将新近开发的生物标志物海冰代用指标IP25（biomarker sea-ice proxy）应用于过去18000年西北太平洋与白令海西部海域海冰分布范围及其变化的高分辨率重建。为明确海冰变化的控制机制，本研究将IP25数据与已发表的海表温度（sea-surface temperature）、硅藻及生物成因蛋白石数据进行关联分析。研究结果显示，在冷期（海因里希冰阶1与新仙女木事件期间），研究区域存在季节性海冰覆盖；而在暖期（博林-阿勒罗德暖期与全新世），研究区域则以海冰减少或无冰环境为主。海冰分布范围的变化似乎与调控亚北极太平洋与白令海之间海洋环流的气候异常及海平面变化密切相关，尤以通过阿留申海峡注入的阿拉斯加海流的影响最为显著。