基于神农架青天洞石笋两个230Th年龄、582条纹层计数和183个氧同位素数据,重建了7～6 ka B.P.期间平均3年分辨率的1δ8O变化序列。持续约580年振幅达1.8‰的δ18O在平均值-9.66‰上下波动,指示了东亚季风降水强度的长期演化趋势和高频...基于神农架青天洞石笋两个230Th年龄、582条纹层计数和183个氧同位素数据,重建了7～6 ka B.P.期间平均3年分辨率的1δ8O变化序列。持续约580年振幅达1.8‰的δ18O在平均值-9.66‰上下波动,指示了东亚季风降水强度的长期演化趋势和高频振荡信息,大致划分为4个百年尺度旋回。青天洞与阿曼石笋δ18O记录的对比表明,东亚季风和印度季风在百年或更短时间尺度上同相位变化,可能反映了两地季风气候受统一的印度洋/太平洋大尺度水汽循环控制。功率谱分析揭示出163、81、16和11年的周期,大致与树轮Δ14C百年至数十年尺度太阳活动变化周期相同。展开更多
Seven U-Th dates, 560 δ 18O data and microscopic sequences were measured for sta- lagmites from two high-altitude caves in Shennongjia area, Hubei Province. Variations of the de- cadal-resolution stalagmite δ 18O re...Seven U-Th dates, 560 δ 18O data and microscopic sequences were measured for sta- lagmites from two high-altitude caves in Shennongjia area, Hubei Province. Variations of the de- cadal-resolution stalagmite δ 18O record from Swan Cave (1600 m elevation) reflect large spatial changes in circulation strength and precipitation of Asian monsoon. The evidence comes from a great similarity among the stalagmite δ 18O records from Nanjing, Jiangsu Province; Libo, Guizhou Province and here studied area during the last deglaciation, including a part interval of Younger-Dryas event and Bolling-Allerod. A 30-year-resolution stalagmite δ 18O record from Yongxing Cave (1400 m eleva- tion), 70 km away from Swan Cave, reveals a rapid transition of Asian monsoon climate during Ter- mination 3 at about 245±5 kaBP. Based on 3 U-Th dates and about 5000 continuous annual bands, a millennial dry episode has been observed during Asian monsoonal Termination 3 from the Yongxing δ 18O profile. With respect to its structure, duration and transition, the dry reversal, as indicated by our stalagmite δ 18O record, generally agrees with the pattern of the YD event well-expressed in the Chi- nese stalagmite δ 18O records. This YD-type event is characterized by a large decrease in δ 18O value as much as 2.30‰, more than half of the δ 18O excursion between glacial/interglacial periods, and lasts 1371±59 a determined by the annual counting chronology. After this event, the monsoon climate shifted abruptly into the interglacial period within 74±4 a. Our data corroborate the view that the re- peated occurrence of YD-type event was not an “accident”, possibly resulted from the coupling of ice-sheet and oceanic/atmospheric circulations.展开更多
Based on 23 U/Th analyses and 532 oxygen isotopic data, an averaged 80-a stalagmite oxygen isotopic composition series was established through 95 to 56 thousand years before present (ka BP) from two speleothems in Sha...Based on 23 U/Th analyses and 532 oxygen isotopic data, an averaged 80-a stalagmite oxygen isotopic composition series was established through 95 to 56 thousand years before present (ka BP) from two speleothems in Shanbao Cave, Shennongjia, central China. Shanbao Cave record (referred to as SB record) replicates well with Hulu Cave record, extending the characteristics of millennial oscillations in East-Asian-Summer-Monsoon (EASM) to the past 95 ka. The trend of the SB record generally follows mid-July solar insolation at 65°N, suggesting that mid-high northern latitude insolation, in the first or- der, controls changes of EASM intensity. Millennial oscillations of EASM recorded in the stalagmites are well related to the Greenland interstadials referred to as Dansgaard/Oeschger (D/O) events from 1 to 22, indicating that rapid ocean-atmosphere reorganization in North Atlantic has a remote effect in EASM. The well-dated D/O events by stalagmites probably provide an absolute calibration for chro- nologies of Greenland ice cores. The timings of D/O events in the SB record are different variously from those in Greenland ice cores. For D/O 19 and 20, the age offsets between the stalagmites' and the Greenland ice cores' record are significant, larger than the uncertainties of uranium-series dating. The two events in the SB record are younger than those in North GRIP time scale by 1―2 ka, and older than the counterparts in GISP2 by approximately 3―4 ka. A comparison between the SB and Brazil stalag- mite record shows an anti-phase relation in millennial-scale monsoon precipitation between the two localities. This supports a mode for the coupled ocean-atmosphere "See-saw".展开更多
从 Sanbao 洞的一个石笋氧同位素记录，中国，与 7 230Th 年龄和 355 氧同位素数据建立了，在现在( ka BP )前从 284～240 千年为时期向东方亚洲季风(电动会计记帐机)紧张的连续历史提供 34 ka 的典型错误。这个新记录扩大以前出版...从 Sanbao 洞的一个石笋氧同位素记录，中国，与 7 230Th 年龄和 355 氧同位素数据建立了，在现在( ka BP )前从 284～240 千年为时期向东方亚洲季风(电动会计记帐机)紧张的连续历史提供 34 ka 的典型错误。这个新记录扩大以前出版的石笋 18O 记录回到海洋的氧同位素阶段(MIS ) 8。MIS8 电动会计记帐机记录广泛地跟随导致 orbitally 的曝晒变化并且被至少 6 标点强壮 -- 并且 3 个弱季风的事件。在结束 III (TIII ) 附近的弱季风事件在 257 ka BP， 253 ka BP 和 246 ka BP 被标明日期，并且能清楚地被相关到三冰木排碎片(IRD ) 在北方大西洋的事件。TIII 看起来显示二阶段的冰川的结束进程，类似于 TI 和 TII 的。阶段我被与完整的大气的 CO2 集中和南极温度上升是同时代的几几千年(250244 ka BP ) 的一个弱季风阶段描绘。阶段 II 被很快加强的季风在 244 ka BP 标记，由 CH4 集中和大气的 CO2 集中的快速的增加伴随了。我们的观察支持北半球(NH ) 夏天曝晒触发了的 Milankovitch 理论冰川间冰期的周期。另外，我们的结果建议南部的半球(嘘) 温暖可能在 TIII 便于 AM 的结束。展开更多
文摘基于神农架青天洞石笋两个230Th年龄、582条纹层计数和183个氧同位素数据,重建了7～6 ka B.P.期间平均3年分辨率的1δ8O变化序列。持续约580年振幅达1.8‰的δ18O在平均值-9.66‰上下波动,指示了东亚季风降水强度的长期演化趋势和高频振荡信息,大致划分为4个百年尺度旋回。青天洞与阿曼石笋δ18O记录的对比表明,东亚季风和印度季风在百年或更短时间尺度上同相位变化,可能反映了两地季风气候受统一的印度洋/太平洋大尺度水汽循环控制。功率谱分析揭示出163、81、16和11年的周期,大致与树轮Δ14C百年至数十年尺度太阳活动变化周期相同。
基金This work was supported by the National Natural Science Foundation of China(Grant No.40225007)the Innovation Project in Graduate Education of Jiangsu Province.
文摘Seven U-Th dates, 560 δ 18O data and microscopic sequences were measured for sta- lagmites from two high-altitude caves in Shennongjia area, Hubei Province. Variations of the de- cadal-resolution stalagmite δ 18O record from Swan Cave (1600 m elevation) reflect large spatial changes in circulation strength and precipitation of Asian monsoon. The evidence comes from a great similarity among the stalagmite δ 18O records from Nanjing, Jiangsu Province; Libo, Guizhou Province and here studied area during the last deglaciation, including a part interval of Younger-Dryas event and Bolling-Allerod. A 30-year-resolution stalagmite δ 18O record from Yongxing Cave (1400 m eleva- tion), 70 km away from Swan Cave, reveals a rapid transition of Asian monsoon climate during Ter- mination 3 at about 245±5 kaBP. Based on 3 U-Th dates and about 5000 continuous annual bands, a millennial dry episode has been observed during Asian monsoonal Termination 3 from the Yongxing δ 18O profile. With respect to its structure, duration and transition, the dry reversal, as indicated by our stalagmite δ 18O record, generally agrees with the pattern of the YD event well-expressed in the Chi- nese stalagmite δ 18O records. This YD-type event is characterized by a large decrease in δ 18O value as much as 2.30‰, more than half of the δ 18O excursion between glacial/interglacial periods, and lasts 1371±59 a determined by the annual counting chronology. After this event, the monsoon climate shifted abruptly into the interglacial period within 74±4 a. Our data corroborate the view that the re- peated occurrence of YD-type event was not an “accident”, possibly resulted from the coupling of ice-sheet and oceanic/atmospheric circulations.
基金Supported by the Foundation for the Author of National Excellent Doctoral Disserta-tion of China(FANEDD,No.200227)China National Outstanding Youth Science Foundation(Grant No.40225007)
文摘Based on 23 U/Th analyses and 532 oxygen isotopic data, an averaged 80-a stalagmite oxygen isotopic composition series was established through 95 to 56 thousand years before present (ka BP) from two speleothems in Shanbao Cave, Shennongjia, central China. Shanbao Cave record (referred to as SB record) replicates well with Hulu Cave record, extending the characteristics of millennial oscillations in East-Asian-Summer-Monsoon (EASM) to the past 95 ka. The trend of the SB record generally follows mid-July solar insolation at 65°N, suggesting that mid-high northern latitude insolation, in the first or- der, controls changes of EASM intensity. Millennial oscillations of EASM recorded in the stalagmites are well related to the Greenland interstadials referred to as Dansgaard/Oeschger (D/O) events from 1 to 22, indicating that rapid ocean-atmosphere reorganization in North Atlantic has a remote effect in EASM. The well-dated D/O events by stalagmites probably provide an absolute calibration for chro- nologies of Greenland ice cores. The timings of D/O events in the SB record are different variously from those in Greenland ice cores. For D/O 19 and 20, the age offsets between the stalagmites' and the Greenland ice cores' record are significant, larger than the uncertainties of uranium-series dating. The two events in the SB record are younger than those in North GRIP time scale by 1―2 ka, and older than the counterparts in GISP2 by approximately 3―4 ka. A comparison between the SB and Brazil stalag- mite record shows an anti-phase relation in millennial-scale monsoon precipitation between the two localities. This supports a mode for the coupled ocean-atmosphere "See-saw".
基金supported by the National Natural Science Foundation of China (Grant Nos. 40631003 and 40771009) Innovation Project in Graduate Education of Jiangsu Province (Grant No. CX07B-051Z)
文摘从 Sanbao 洞的一个石笋氧同位素记录，中国，与 7 230Th 年龄和 355 氧同位素数据建立了，在现在( ka BP )前从 284～240 千年为时期向东方亚洲季风(电动会计记帐机)紧张的连续历史提供 34 ka 的典型错误。这个新记录扩大以前出版的石笋 18O 记录回到海洋的氧同位素阶段(MIS ) 8。MIS8 电动会计记帐机记录广泛地跟随导致 orbitally 的曝晒变化并且被至少 6 标点强壮 -- 并且 3 个弱季风的事件。在结束 III (TIII ) 附近的弱季风事件在 257 ka BP， 253 ka BP 和 246 ka BP 被标明日期，并且能清楚地被相关到三冰木排碎片(IRD ) 在北方大西洋的事件。TIII 看起来显示二阶段的冰川的结束进程，类似于 TI 和 TII 的。阶段我被与完整的大气的 CO2 集中和南极温度上升是同时代的几几千年(250244 ka BP ) 的一个弱季风阶段描绘。阶段 II 被很快加强的季风在 244 ka BP 标记，由 CH4 集中和大气的 CO2 集中的快速的增加伴随了。我们的观察支持北半球(NH ) 夏天曝晒触发了的 Milankovitch 理论冰川间冰期的周期。另外，我们的结果建议南部的半球(嘘) 温暖可能在 TIII 便于 AM 的结束。
