《科学》论文：冰期海洋环流突变恢复耗时以世纪计而非数十年，中国与印度石笋年层记录显示转变平均约180年
一项发表于《科学》期刊的研究显示，冰期中大西洋经向翻转环流（AMOC）的突发性恢复过程耗时以世纪计，而不是此前依据冰芯记录推断的数十年。论文由董希宇（Xiyu Dong）等人完成，Phys.org 于11月5日作了报道，研究材料由西安交通大学提供。
研究针对的是 Dansgaard–Oeschger（DO）暖事件：这类事件中北半球高纬度气温上升5至16摄氏度，与 AMOC 增强密切相关，常被用作推演未来 AMOC 变化的参照。此前研究认为 DO 事件中 AMOC 的增强在数十年内完成，但这一判断倚赖格陵兰冰芯的氧同位素（δ¹⁸O）信号，而该信号同时受气温与水汽来源影响。本次研究改用直接响应 AMOC 变化的亚洲季风区石笋记录：印度东北部 Cherrapunji 洞与中国西南 Shuixi 洞两份具清晰年层的石笋，结合已发表的 Zhangjia 洞记录，得到覆盖 DO-1 至 DO-8 的高分辨率 δ¹⁸O 序列。结果显示，各次转变持续时间一致地超过100年、平均约180年，远长于格陵兰冰芯 δ¹⁸O 所显示的十年尺度变化。
第一作者董希宇表示，本次所用石笋年层清晰，铀钍定年给出精确的绝对年代，但相对年代须靠年层约束，才能精确测定每次转变的持续时长并与格陵兰冰芯记录直接对比。同位素气候模型模拟进一步显示这是一个两阶段过程：先是北大西洋东北部海冰退缩触发区域大气环流快速调整，造成格陵兰 δ¹⁸O 的陡升；随后 AMOC 继续增强、西北部海冰继续退缩，但大气环流型态与水汽输送路径不再显著改变，格陵兰 δ¹⁸O 也就不再大幅波动—亚洲石笋记录捕捉到了 AMOC 增强的完整过程。程海教授表示，该研究厘清了亚洲石笋 δ¹⁸O、格陵兰冰芯 δ¹⁸O 与 AMOC 三者的关系。董希宇同时表示，这意味着在讨论未来 AMOC 临界转变风险时，需要更清楚地说明转变将持续多久；作者团队并指出，后续仍需更多高质量的 DO 事件石笋记录、北大西洋海冰重建与纳入冰盖过程的气候模型。
Science Study: Glacial Ocean Circulation Recoveries Took Centuries, Not Decades; Speleothem Annual Layers From China and India Put Transitions at About 180 Year
A study published in Science has found that abrupt recoveries of the Atlantic meridional overturning circulation (AMOC) during the last ice age took centuries rather than the decades previously inferred from ice-core records. The paper, by Xiyu Dong and colleagues, was reported by Phys.org on November 5, with material provided by Xi'an Jiaotong University.
The work concerns Dansgaard–Oeschger (DO) warm events, during which high-latitude Northern Hemisphere temperatures rose by 5–16 °C in close connection with a strengthening AMOC; the events are widely used as an analog for future AMOC change. Existing studies suggested AMOC strengthening during DO events occurred within decades, but that rested on Greenland ice-core δ¹⁸O records, a signal influenced by both temperature and moisture source. The new study instead used speleothem records that respond directly to AMOC-driven changes: two annually laminated speleothems from Cherrapunji Cave in northeast India and Shuixi Cave in southwest China, together with published records from Zhangjia Cave, yielded high-resolution δ¹⁸O series spanning events DO-1 to DO-8. The transitions consistently lasted longer than 100 years, averaging about 180 years — far longer than the decadal-scale shifts in Greenland ice-core δ¹⁸O records.
First author Xiyu Dong said the speleothems' clear annual laminae were essential: uranium–thorium dating gives precise absolute ages but cannot give reliable relative ages, whereas the annual layers precisely constrain how long each transition lasted and allow direct comparison with the Greenland records. Isotope-enabled climate modeling showed a two-stage process: retreat of sea ice in the northeastern North Atlantic first triggered a rapid adjustment of regional atmospheric circulation, causing the sharp rise in Greenland δ¹⁸O; the AMOC then strengthened further and sea ice in the northwestern North Atlantic continued to retreat, but atmospheric circulation modes and moisture transport pathways did not change significantly, so Greenland δ¹⁸O showed no further marked fluctuation — meaning the Asian monsoon speleothem records capture the full AMOC strengthening process. Professor Hai Cheng said the work clarifies the relationship between Asian speleothem δ¹⁸O, Greenland ice-core δ¹⁸O and the AMOC. Dong added that when discussing the risk of a future AMOC tipping point, researchers need to be clearer about how long such a transition would take. The authors also emphasized that more high-quality speleothem records of DO events, reconstructions of North Atlantic sea ice, and climate models integrating ice-sheet processes will be essential to further understanding of abrupt climate change.
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来源：《科学》期刊论文（经 Phys.org 报道
发布：GSM·美国（发布链接）
图片来源：洞穴内的石笋与钟乳石（资料图）。（Wikimedia Commons／CC BY-SA 3.0）|Stalagmites and stalactites inside a cave (file photo). (Wikimedia Commons / CC BY-SA 3.0)
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