The South Pole Ice Core (SPICEcore) chronology and supporting data

The South Pole Ice Core (SPICEcore) was drilled in 2014-2016 to provide a detailed multi-proxy archive of paleoclimate conditions in East Antarctica during the Holocene and late Pleistocene. Interpretation of these records requires an accurate depth-age relationship. Here, we present the SP19 timescale for the age of the ice of SPICEcore. SP19 is synchronized to the WD2014 chronology from the West Antarctic Ice Sheet Divide (WAIS Divide) ice core using stratigraphic matching of 251 volcanic events. These events indicate an age of 54,302 +/- 519 years BP (before the year 1950) at the bottom of SPICEcore. Annual layers identified in sodium and magnesium ions to 11,341 BP were used to interpolate between stratigraphic volcanic tie points, yielding an annually-resolved chronology through the Holocene. Estimated timescale uncertainty during the Holocene is less than 18 years relative to WD2014, with the exception of the interval between 1800 to 3100 BP when uncertainty estimates reach +/- 25 years due to widely spaced volcanic tie points. Prior to the Holocene, uncertainties remain within 124 years relative to WD2014. Results show an average Holocene accumulation rate of 7.4 cm/yr (water equivalent). The time variability of accumulation rate is consistent with expectations for steady-state ice flow through the modern spatial pattern of accumulation rate. Time variations in nitrate concentration, nitrate seasonal amplitude, and δ15N of N2 in turn are as expected for the accumulation-rate variations. The highly variable yet well-constrained Holocene accumulation history at the site can help improve scientific understanding of deposition-sensitive climate proxies such as δ15N of N2 and photolyzed chemical compounds.

南极冰芯（South Pole Ice Core, SPICEcore）于2014至2016年完成钻探，旨在获取全新世及晚更新世时期东南极洲古气候的高分辨率多代用指标档案。对这些冰芯记录的解译需要精准的深度-年代关系。本文提供了SPICEcore冰体的SP19年代标尺。SP19通过251次火山事件的地层匹配，与西南极冰盖分水岭（West Antarctic Ice Sheet Divide, WAIS Divide）冰芯的WD2014年表实现同步。这些火山事件显示，SPICEcore底部的年代为距今（以1950年为基准）54302±519年。研究以钠、镁离子识别出的11341 BP年层作为约束，在地层火山定标点之间进行内插，由此构建了贯穿全新世的年分辨率年代序列。相较于WD2014年表，全新世时期的年代标尺不确定性小于18年，但1800至3100 BP的时段除外——该区间因火山定标点分布稀疏，不确定性达到±25年。全新世之前的年代不确定性相较于WD2014年表仍控制在124年以内。结果显示，该点位全新世平均冰芯积累率为7.4厘米/年（水当量）。积累率的时间变率与现代积累率的空间分布格局下的稳态冰流预期相符。硝酸盐浓度、硝酸盐季节振幅以及氮气的氮15同位素比值（δ¹⁵N of N₂）的时间变化，也与积累率变化的预期一致。该点位高度可变但约束良好的全新世积累历史，有助于提升学界对沉积敏感型气候代用指标的科学认知，例如氮气的氮15同位素比值以及光解化学组分。