本研究基于云南香格里拉石卡雪山高原面洞穴钙板SK下部约8.2 cm厚的7个^(230)Th年龄、81组碳氧同位素和9个Δ47温度数据,恢复了MIS 7.2时段的气候变化历史。SK-δ^(18)O序列重建了213.75~199.74 ka B.P.时段的印度夏季风演变过程,平均...本研究基于云南香格里拉石卡雪山高原面洞穴钙板SK下部约8.2 cm厚的7个^(230)Th年龄、81组碳氧同位素和9个Δ47温度数据,恢复了MIS 7.2时段的气候变化历史。SK-δ^(18)O序列重建了213.75~199.74 ka B.P.时段的印度夏季风演变过程,平均分辨率约180 a,该序列显示δ^(18)O值在209.17 ka B.P.和205.00 ka B.P.前后显著正偏,清晰记录了两个千年尺度季风减弱事件。通过与亚洲季风区石笋记录的对比发现,在MIS 7.2开始阶段印度夏季风与东亚夏季风同步变化,但在结束阶段,SK记录早于三宝洞记录约4000 a,考虑到样品年代误差及分辨率等因素,认为该时段轨道尺度上亚洲季风具有一致变化,但是准确时间还有待进一步厘清。Δ47古温度曲线与δ^(18)O、δ^(13)C记录的对比显示出MIS 7.2结束时段水热异步变化特征,与黄土-古土壤序列结论类似,不同的是SK记录的温度直接响应北半球太阳辐照度变化,而不是响应南极温度变化。SK记录显示夏季温度从207.36 ka B.P.左右逐渐回升,同期印度夏季风缓慢增强,但被大幅度的千年尺度季风减弱事件中断,印度夏季风显著增强滞后温度变化约6000 a,该过程与末次消冰期中海因里希事件(Heinrich events)或新仙女木事件(YD)类似,其机制可能与高纬气候变化有关,即冰盖融解导致大量淡水注入北大西洋,影响了北大西洋深水(NADW)和南极底层流(AABW)的生成,从而导致温盐环流(THC)减弱或中断,并通过大气-海洋环流传递到低纬地区,触发千年尺度印度夏季风减弱事件。展开更多
The influence of metal cations on 13C-18O bonds in carbonates is still under debate. This paper used ab initio method to investigate this kind of influence of Mg2+, Fe2+ and Zn2+ cations on 13C-18O bonds in precipitat...The influence of metal cations on 13C-18O bonds in carbonates is still under debate. This paper used ab initio method to investigate this kind of influence of Mg2+, Fe2+ and Zn2+ cations on 13C-18O bonds in precipitated aragonite, calcite and dolomite. The polynomials of Δ47 and reduced partition function ratios (RPFRs) for 13/12C, 14/12C and 18/16O of these minerals were given within temperatures ranging from 260 to 1500 K. We found that these cations significantly decreased the Δ47 values at the level of 10-3 - 10-2 per mil, comparing with pure crystals;and that if the Δ47 values were used to reconstruct the temperatures Ts, the deviation of T was about 7.2°C for, for instance, zinc-enriched aragonite, as discussed in our paper. It was suggested that due to such influence, researchers would better use a proper thermometer according to the main impurity metal cations in carbonates. We also found that according to the probability theory, the theoretical value of the influence of phosphoric acid on Δ47 of CO2 degassed from different carbonates was zero.展开更多
文摘本研究基于云南香格里拉石卡雪山高原面洞穴钙板SK下部约8.2 cm厚的7个^(230)Th年龄、81组碳氧同位素和9个Δ47温度数据,恢复了MIS 7.2时段的气候变化历史。SK-δ^(18)O序列重建了213.75~199.74 ka B.P.时段的印度夏季风演变过程,平均分辨率约180 a,该序列显示δ^(18)O值在209.17 ka B.P.和205.00 ka B.P.前后显著正偏,清晰记录了两个千年尺度季风减弱事件。通过与亚洲季风区石笋记录的对比发现,在MIS 7.2开始阶段印度夏季风与东亚夏季风同步变化,但在结束阶段,SK记录早于三宝洞记录约4000 a,考虑到样品年代误差及分辨率等因素,认为该时段轨道尺度上亚洲季风具有一致变化,但是准确时间还有待进一步厘清。Δ47古温度曲线与δ^(18)O、δ^(13)C记录的对比显示出MIS 7.2结束时段水热异步变化特征,与黄土-古土壤序列结论类似,不同的是SK记录的温度直接响应北半球太阳辐照度变化,而不是响应南极温度变化。SK记录显示夏季温度从207.36 ka B.P.左右逐渐回升,同期印度夏季风缓慢增强,但被大幅度的千年尺度季风减弱事件中断,印度夏季风显著增强滞后温度变化约6000 a,该过程与末次消冰期中海因里希事件(Heinrich events)或新仙女木事件(YD)类似,其机制可能与高纬气候变化有关,即冰盖融解导致大量淡水注入北大西洋,影响了北大西洋深水(NADW)和南极底层流(AABW)的生成,从而导致温盐环流(THC)减弱或中断,并通过大气-海洋环流传递到低纬地区,触发千年尺度印度夏季风减弱事件。
文摘The influence of metal cations on 13C-18O bonds in carbonates is still under debate. This paper used ab initio method to investigate this kind of influence of Mg2+, Fe2+ and Zn2+ cations on 13C-18O bonds in precipitated aragonite, calcite and dolomite. The polynomials of Δ47 and reduced partition function ratios (RPFRs) for 13/12C, 14/12C and 18/16O of these minerals were given within temperatures ranging from 260 to 1500 K. We found that these cations significantly decreased the Δ47 values at the level of 10-3 - 10-2 per mil, comparing with pure crystals;and that if the Δ47 values were used to reconstruct the temperatures Ts, the deviation of T was about 7.2°C for, for instance, zinc-enriched aragonite, as discussed in our paper. It was suggested that due to such influence, researchers would better use a proper thermometer according to the main impurity metal cations in carbonates. We also found that according to the probability theory, the theoretical value of the influence of phosphoric acid on Δ47 of CO2 degassed from different carbonates was zero.
