Annual-layer thickness, δ¹⁸O and sodium values on Akademii Nauk ice core (AD 900-1998) based on core chronology AN 2012@en

Understanding recent Arctic climate change requires detailed information on past changes, in particular on a regional scale. The extension of the depth–age relation of the Akademii Nauk (AN) ice core from Severnaya Zemlya (SZ) to the last 1100 yr provides new perspectives on past climate fluctuations in the Barents and Kara seas region. Here, we present the easternmost high-resolution ice-core climate proxy records (d18O and sodium) from the Arctic. Multi-annual AN d18O data as near-surface air-temperature proxies reveal major temperature changes over the last millennium, including the absolute minimum around 1800 and the unprecedented warming to a double-peak maximum in the early 20th century. The long-term cooling trend in d18O is related to a decline in summer insolation but also to the growth of the AN ice cap as indicated by decreasing sodium concentrations. Neither a pronounced Medieval Climate Anomaly nor a Little Ice Age are detectable in the AN d18O record. In contrast, there is evidence of several abrupt warming and cooling events, such as in the 15th and 16th centuries, partly accompanied by corresponding changes in sodium concentrations. These abrupt changes are assumed to be related to sea-ice cover variability in the Barents and Kara seas region, which might be caused by shifts in atmospheric circulation patterns. Our results indicate a significant impact of internal climate variability on Arctic climate change in the last millennium.要理解近期北极气候变化，需获取过往气候变化的详细信息，尤其是区域尺度上的相关数据。将北地群岛（Severnaya Zemlya, SZ）的科学院（Akademii Nauk, AN）冰芯的深度-年龄关系延伸至过去1100年，为巴伦支海与喀拉海区域的过往气候波动研究提供了全新视角。本研究披露了北极地区最东端的高分辨率冰芯气候代用指标记录（δ¹⁸O与钠元素浓度）。作为近地表气温代用指标的多年际AN冰芯δ¹⁸O数据，揭示了过去千年间的显著温度变化，包括约1800年前后的绝对温度极小值，以及20世纪早期升温至双峰峰值的前所未有的变暖过程。δ¹⁸O记录所反映的长期变冷趋势，既与夏季太阳辐射量下降相关，也与钠元素浓度降低所指示的AN冰盖扩张有关。AN冰芯的δ¹⁸O记录中，既未检出显著的中世纪暖期（Medieval Climate Anomaly）信号，也未发现小冰期（Little Ice Age）的特征。与之相反，记录中存在多起突发性冷暖事件，例如15至16世纪的冷暖波动，其中部分事件伴随钠元素浓度的相应变化。这些突发性气候波动被认为与巴伦支海-喀拉海区域的海冰覆盖变化相关，而该变化可能由大气环流模式的转变所驱动。本研究结果表明，内部气候变率对过去千年的北极气候变化具有显著影响。