Last Interglacial synthesis of high-latitude temperature: temperature anomalies and associated errors for 4 time slices@en

The Last Interglacial (LIG, 129-116 thousand of years BP, ka) represents a test bed for climate model feedbacks in warmer-than-present high latitude regions. However, mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial, a spatio-temporal picture of LIG temperature changes is difficult to obtain. Here, we have selected 47 polar ice core and sub-polar marine sediment records and developed a strategy to align them onto the recent AICC2012 ice core chronology. We provide the first compilation of high-latitude temperature changes across the LIG associated with a coherent temporal framework built between ice core and marine sediment records. Our new data synthesis highlights non-synchronous maximum temperature changes between the two hemispheres with the Southern Ocean and Antarctica records showing an early warming compared to North Atlantic records. We also observe warmer than present-day conditions that occur for a longer time period in southern high latitudes than in northern high latitudes. Finally, the amplitude of temperature changes at high northern latitudes is larger compared to high southern latitude temperature changes recorded at the onset and the demise of the LIG. We have also compiled four data-based time slices with temperature anomalies (compared to present-day conditions) at 115 ka, 120 ka, 125 ka and 130 ka and quantitatively estimated temperature uncertainties that include relative dating errors. This provides an improved benchmark for performing more robust model-data comparison. The surface temperature simulated by two General Circulation Models (CCSM3 and HadCM3) for 130 ka and 125 ka is compared to the corresponding time slice data synthesis. This comparison shows that the models predict warmer than present conditions earlier than documented in the North Atlantic, while neither model is able to produce the reconstructed early Southern Ocean and Antarctic warming. Our results highlight the importance of producing a sequence of time slices rather than one single time slice averaging the LIG climate conditions.末次间冰期（Last Interglacial, LIG，129~116 ka BP）是研究暖于现代的高纬度地区气候模型反馈机制的理想试验平台。然而，由于整合全球不同区域的古气候档案并非易事，获取LIG温度变化的完整时空分布图景颇具挑战。本研究筛选了47份极地冰芯与亚极地海洋沉积记录，并开发了一套将这些记录校准至最新AICC2012冰芯年代框架的方法。我们首次构建了关联冰芯与海洋沉积记录的统一时间标尺，并据此汇编了LIG时期高纬度温度变化的首个综合数据集。本次全新的数据综合分析显示，南北半球的温度峰值出现时间并不同步：南大洋与南极的记录较北大西洋记录更早出现暖化。同时我们观察到，南半球高纬度地区的暖于现代的气候持续时长，要长于北半球高纬度地区。此外，在末次间冰期的起始与消亡阶段，北半球高纬度地区的温度变化幅度，要大于南半球高纬度地区的对应记录。我们还汇编了四个基于观测数据的时间切片数据集，分别对应115 ka、120 ka、125 ka与130 ka的温度距平（以现代气候条件为参照），并定量估算了包含相对测年误差在内的温度不确定性。这一工作为开展更严谨的模型-数据对比提供了优化后的基准。我们将两个通用环流模型（General Circulation Models, GCM）在130 ka与125 ka时段模拟的地表温度，与对应时间切片的综合数据进行了对比。对比结果显示，相较于北大西洋的重建记录，模型预测的暖于现代的气候出现时间更早；但两款模型均无法再现南大洋与南极的早期暖化现象。我们的研究结果凸显了构建时间切片序列而非单一平均化的末次间冰期气候条件单一切片的重要性。