Based on MC-ICP-MS U-series dating and stable O-isotope analysis results, a 4―5 years resolution monsoon record over the past 1000 years has been estab- lished for two stalagmites from Dongge Cave, Guizhou. The high ...Based on MC-ICP-MS U-series dating and stable O-isotope analysis results, a 4―5 years resolution monsoon record over the past 1000 years has been estab- lished for two stalagmites from Dongge Cave, Guizhou. The high resolution oxygen isotope record serves as a proxy for variations in rainfall of Asian southwest monsoon over the Yunnan-Guizhou Plateau. A close relation of the δ 18O record with the ?14C record from tree rings largely reflects impact of centennial-scale solar activity on the monsoon climate changes. The conspicuous decrease in the δ 18O value at AD 1720 indicates an abrupt increase in monsoon rainfall, sug- gesting that an atmospheric-oceanic couple over the tropical Indian Ocean plays an important role in rapid increase of the Northern Hemisphere temperature over the last century.展开更多
A glacial stalagmite chronology from Nanjing has been established by the TIMS-U series dating and annual band counting methods. The annually layering sequence spanning the 3000-year period from 18179 to 14900 calendar...A glacial stalagmite chronology from Nanjing has been established by the TIMS-U series dating and annual band counting methods. The annually layering sequence spanning the 3000-year period from 18179 to 14900 calendar years before the present (aBP) was analyzed for evidence of East Asian summer monsoon precipitation variability during the Last Glacial Maximum (LGM). Power spectral analysis of the sequence shows a distinct interannual (2—7 years) band of enhanced variability suggestive of El Ni駉-Southern Oscillation (ENSO) teleconnections into East China during the LGM when climatic boundary conditions were different from those of today. The lower frequency bands (4—7 years) variability becomes weaker from 18179 to 14900 aBP, sup-porting the precession forcing model. The reappearance of the ENSO band in the coldest climatic boundary conditions during the Heinrich Event 1, however, suggests the stimula-tion of the enhanced East Asia winter monsoon to the El Ni駉 events.展开更多
Global abrupt climate changes have been documented by various climate records, including ice cores, ocean sediment cores, lake sediment cores, cave deposits, loess deposits and pollen records. The climate system prefe...Global abrupt climate changes have been documented by various climate records, including ice cores, ocean sediment cores, lake sediment cores, cave deposits, loess deposits and pollen records. The climate system prefers to be in one of two stable states, i.e. interstadial or stadial conditions, but not in between. The transition between two states has an abrupt character. Abrupt climate changes are, in general, synchronous in the northern hemisphere and tropical regions. The timescale for abrupt climate changes can be as short as a decade. As the impacts may be poten-tially serious, we need to take actions such as reducing CO2 emissions to the atmosphere.展开更多
The time sequence of high-resolution paleoclimatic changes since the last glacial period--60,500 yr B.P.--has been reconstructed with high-precision TIMS-U series dates and analyses of the oxygen isotopes from Q4 and ...The time sequence of high-resolution paleoclimatic changes since the last glacial period--60,500 yr B.P.--has been reconstructed with high-precision TIMS-U series dates and analyses of the oxygen isotopes from Q4 and Q6 stalagmites of the Qixin Cave in southern Guizhou. Comparative analyses of δ^18O curves from the GISP2' ice core and the two stalagmites shows that the depositional records of the Dansgaard-Oeschger cycle events 1-18 and Heinrich's events H1-H5 from the records of the two stalagmites reflect rapid climate changes over a short time scale since the last glacial stage, and indicates the precise boundary lines at which the cold events occurred. The study results have shown that the records of the cold and warm events from the two stalagmites since 60,500 yr B.P. are the reflection of the paleo-monsoon circulation. Changes are clearly affected by the climate oscillation of the North Atlantic Ocean, and indicate that they have a strong teleconnection with the paleoclimate changes that occurred in the North Polar region. The records of δ^18O from the Q4 and Q6 stalagmites indicate that the δ^18O values from 60,590 yr B.P. to 11,290 yr B.P. changed from a more negative (or lighter)drift to a heavier or positive drift trend in the last glacial period. The data reflect the weakening of the Asian summer monsoon and the climate which generally became drier and cooler.展开更多
基金This work was supported by the National Outstanding Youth Foundation of China(Grant No.40225007)the 973 Project(Grant No.2004CB20204).
文摘Based on MC-ICP-MS U-series dating and stable O-isotope analysis results, a 4―5 years resolution monsoon record over the past 1000 years has been estab- lished for two stalagmites from Dongge Cave, Guizhou. The high resolution oxygen isotope record serves as a proxy for variations in rainfall of Asian southwest monsoon over the Yunnan-Guizhou Plateau. A close relation of the δ 18O record with the ?14C record from tree rings largely reflects impact of centennial-scale solar activity on the monsoon climate changes. The conspicuous decrease in the δ 18O value at AD 1720 indicates an abrupt increase in monsoon rainfall, sug- gesting that an atmospheric-oceanic couple over the tropical Indian Ocean plays an important role in rapid increase of the Northern Hemisphere temperature over the last century.
基金the National Natural Science Foundation of China (Grant No. 40225007)
文摘A glacial stalagmite chronology from Nanjing has been established by the TIMS-U series dating and annual band counting methods. The annually layering sequence spanning the 3000-year period from 18179 to 14900 calendar years before the present (aBP) was analyzed for evidence of East Asian summer monsoon precipitation variability during the Last Glacial Maximum (LGM). Power spectral analysis of the sequence shows a distinct interannual (2—7 years) band of enhanced variability suggestive of El Ni駉-Southern Oscillation (ENSO) teleconnections into East China during the LGM when climatic boundary conditions were different from those of today. The lower frequency bands (4—7 years) variability becomes weaker from 18179 to 14900 aBP, sup-porting the precession forcing model. The reappearance of the ENSO band in the coldest climatic boundary conditions during the Heinrich Event 1, however, suggests the stimula-tion of the enhanced East Asia winter monsoon to the El Ni駉 events.
文摘Global abrupt climate changes have been documented by various climate records, including ice cores, ocean sediment cores, lake sediment cores, cave deposits, loess deposits and pollen records. The climate system prefers to be in one of two stable states, i.e. interstadial or stadial conditions, but not in between. The transition between two states has an abrupt character. Abrupt climate changes are, in general, synchronous in the northern hemisphere and tropical regions. The timescale for abrupt climate changes can be as short as a decade. As the impacts may be poten-tially serious, we need to take actions such as reducing CO2 emissions to the atmosphere.
文摘The time sequence of high-resolution paleoclimatic changes since the last glacial period--60,500 yr B.P.--has been reconstructed with high-precision TIMS-U series dates and analyses of the oxygen isotopes from Q4 and Q6 stalagmites of the Qixin Cave in southern Guizhou. Comparative analyses of δ^18O curves from the GISP2' ice core and the two stalagmites shows that the depositional records of the Dansgaard-Oeschger cycle events 1-18 and Heinrich's events H1-H5 from the records of the two stalagmites reflect rapid climate changes over a short time scale since the last glacial stage, and indicates the precise boundary lines at which the cold events occurred. The study results have shown that the records of the cold and warm events from the two stalagmites since 60,500 yr B.P. are the reflection of the paleo-monsoon circulation. Changes are clearly affected by the climate oscillation of the North Atlantic Ocean, and indicate that they have a strong teleconnection with the paleoclimate changes that occurred in the North Polar region. The records of δ^18O from the Q4 and Q6 stalagmites indicate that the δ^18O values from 60,590 yr B.P. to 11,290 yr B.P. changed from a more negative (or lighter)drift to a heavier or positive drift trend in the last glacial period. The data reflect the weakening of the Asian summer monsoon and the climate which generally became drier and cooler.
