Speleothem fluid inclusion water isotopes and inferred temperatures from Milandre Cave, Switzerland

The reasons for the early Holocene temperature discrepancy between northern hemispheric model simulations and paleoclimate reconstructions—known as the Holocene temperature conundrum—remain unclear. Using hydrogen isotopes of fluid inclusion water extracted from stalagmites from the Milandre Cave in Switzerland, we established a mid-latitude European mean annual temperature reconstruction for the past 14,000 years. Our Milandre Cave fluid inclusion temperature record (MC-FIT) resembles Greenland and Mediterranean sea surface temperature trends but differs from recent reconstructions obtained from biogenic proxies and climate models. The water isotopes are further synchronized with tropical precipitation records, stressing the Northern Hemisphere signature. Our results support the existence of a European Holocene Thermal Maximum and data model temperature discrepancies. Moreover, data-data comparison reveals a significant latitudinal temperature gradient within Europe. Last, the MC-FIT record suggests that seasonal biases in the proxies are not the primary cause of the Holocene temperature conundrum.北半球模式模拟与古气候重建在早全新世温度上存在差异，这一现象被称为全新世温度难题（Holocene temperature conundrum），其成因至今尚未明确。本研究通过提取自瑞士米兰德洞穴（Milandre Cave）石笋中的流体包裹体水的氢同位素，构建了过去14000年欧洲中纬度地区的年平均温度重建序列。我们得到的米兰德洞穴流体包裹体温度记录（MC-FIT）与格陵兰及地中海海表温度的变化趋势相似，但与近期基于生物代用指标及气候模式获得的重建结果存在显著差异。该水同位素序列还与热带降水记录高度同步，进一步凸显了北半球气候信号特征。本研究结果证实了欧洲全新世高温期的存在，同时支持了数据与模式间的温度差异。此外，数据间对比揭示了欧洲内部存在显著的纬度温度梯度。最后，MC-FIT记录表明，代用指标的季节偏差并非全新世温度难题的主要成因。