NOAA/WDS Paleoclimatology - WAIS Divide Ice Core 67,000 Year Atmospheric CO2 Data

During the last glacial period, atmospheric carbon dioxide (CO2) closely followed Antarctic temperature on millennial timescales. This strong correlation between Antarctic climate and atmospheric CO2 has led to suggestions that reorganizations of Southern Ocean circulation and/or biogeochemistry were the dominant cause of these variations. However, recent work also revealed centennial-scale changes in CO2 that appear unrelated to Antarctic climate and may represent additional modes of carbon cycle variability. Here we present a high-resolution CO2 record from the last glacial period from an ice core drilled in West Antarctica. This reconstruction precisely defines the timing of millennial and centennial CO2 variations with respect to Antarctic temperature and abrupt changes in Northern Hemisphere climate during Heinrich stadials and Dansgaard-Oeschger events. On the millennial scale, CO2 tracks Antarctic climate variability, but peak CO2 levels lag peak Antarctic temperature by more than 500 years. Centennial-scale CO2 increases of up to 10 ppm occurred within some Heinrich stadials, and increases of ~5 ppm occurred at the abrupt warming of most Dansgaard-Oeschger events. Regression analysis suggests that the CO2 variations can be explained by a combination of one mechanism operating on the timescale of Antarctic climate variability and a second responding on the timescale of Dansgaard-Oeschger events. Consistent with our statistical analysis, carbon cycle box-model simulations illustrate a plausible scenario where Southern Hemisphere processes contribute the majority of the CO2 variability during the last glacial period, but Northern Hemisphere processes are the crucial drivers of centennial-scale variability.

末次冰期期间，大气二氧化碳(CO₂)在千年尺度上与南极温度呈现紧密的耦合关联。这种南极气候与大气CO₂间的强相关性，催生了相关假说，认为南大洋环流与（或）生物地球化学过程的重组是上述CO₂变化的主导成因。然而，近期研究还发现了百年尺度的CO₂变化，这些变化似乎与南极气候无关，可能代表了碳循环变异的额外模态。

本研究基于西南极钻取的一支冰芯，构建了末次冰期高分辨率的CO₂记录。该重建结果精准界定了千年与百年尺度CO₂变化相对于南极温度，以及海因里希冷期(Heinrich stadials)、丹斯果-奥什格尔事件(Dansgaard-Oeschger events)期间北半球气候突变的时间序列关系。在千年尺度上，CO₂浓度变化追踪南极气候的变异性，但CO₂峰值较南极温度峰值滞后超过500年。部分海因里希冷期内出现了最高达10 ppm的百年尺度CO₂上升，而多数丹斯果-奥什格尔事件的突变增温阶段，则出现了约5 ppm的CO₂浓度上升。

回归分析表明，CO₂的变化可由两种机制共同解释：一种以南极气候变异性的时间尺度运作，另一种则响应丹斯果-奥什格尔事件的时间尺度。与我们的统计分析结果一致，碳循环箱式模型(carbon cycle box-model)模拟结果展示了一种合理情景：末次冰期期间，南半球过程贡献了绝大多数的CO₂变异性，但北半球过程才是百年尺度CO₂变异的关键驱动因素。