Paleoclimate simulations of the mid-Holocene （MH） and Last Glacial maximum （LGM） by the latest versions of the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 and Grid-point Version 2 （FGOA...Paleoclimate simulations of the mid-Holocene （MH） and Last Glacial maximum （LGM） by the latest versions of the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 and Grid-point Version 2 （FGOALS-s2 and g2） are evaluated in this study. The MH is characterized by changes of insolation induced by orbital parameters, and the LGM is a glacial period with large changes in greenhouse gases, sea level and ice sheets. For the MH, both versions of FGOALS simulate reasonable responses to the changes of insolation, such as the enhanced summer monsoon in African-Asian regions. Model differences can be identified at regional and seasonal scales. The global annual mean surface air temperature （TAS） shows no significant change in FGOALS-s2, while FGOALS-g2 shows a global cooling of about 0.7~C that is related with a strong cooling during boreal winter. The amplitude of ENSO is weaker in FGOALS-g2, which agrees with proxy data. For the LGM, FGOALS-g2 captures the features of the cold and dry glacial climate, including a global cooling of 4.6℃ and a decrease in precipitation by 10%. The ENSO is weaker at the LGM, with a tendency of stronger ENSO cold events. Sensitivity analysis shows that the Equilibrium Climate Sensitivity （ECS） estimated for FGOALS ranges between 4.23℃ and 4.59℃. The sensitivity of precipitation to the changes of TAS is -2.3%℃-1, which agrees with previous studies. FGOALS-g2 shows better simulations of the Atlantic Meridional Overturning Circulation （AMOC） and African summer monsoon precipitation in the MH when compared with FGOALS-gl.0; however, it is hard to conclude any improvements for the LGM.展开更多
In this article, Milkov and Sassen＇s model is selected to calculate the thickness of the gas hydrate stable zone （GHSZ） and the amount of gas hydrate in the Xisha （西沙） Trough at present and at the last glacial ...In this article, Milkov and Sassen＇s model is selected to calculate the thickness of the gas hydrate stable zone （GHSZ） and the amount of gas hydrate in the Xisha （西沙） Trough at present and at the last glacial maximum （LGM）, respectively, and the effects of the changes in the bottom water temperature and the sea level on these were also discussed. The average thickness of the GHSZ in Xisha Trough is estimated to be 287 m and 299 m based on the relationship between the GHSZ thickness and the water depth established in this study at present and at LGM, respectively. Then, by assuming that the distributed area of gas hydrates is 8 000 km^2 and that the gas hydrate saturation is 1.2% of the sediment volume, the amounts of gas hydrate are estimated to be -2.76×10^10 m^3 and -2.87×10^10 m^3, and the volumes of hydrate-bound gases are -4.52×10^12 m^3 and -4.71×10^12 m^3 at present and at LGM, respectively. The above results show that the thickness of GHSZ decreases with the bottom water temperature increase and increases with the sea level increase, wherein the effect of the former is larger than that of the latter, that the average thickness of GHSZ in Xisha Trough had been reduced by -12 m, and that 1.9×10^11 m^3 of methane is released from approximately 1.1×10^9m^3 of gas hydrate since LGM. The released methane should have greatly affected the environment.展开更多
The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This pa...The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This paper examines their effects on the current evidence for the timing of past glaciations, and the development and evolution of permafrost. There are two theories regarding glaciation on the Qinghai-Tibet Plateau （QTP）. Kuhle suggested that there was a major, unified ice-cap during the Last Glacial Maximum （LGM）, whereas major Chinese glaciologists and others have not found or verified reliable evidence for this per se. There have been limited glaciations during the last 1.1 Ma B.P. but with increasing dominance of permafrost including both primary and secondary tessellons infilled with rock, sand or loess. The East Asia Monsoon was absent in this area during the main LGM, starting at 〉30 ka B.P. on the plateau, with sufficient precipitation reappearing about 19 ka B.P. to produce ice-wedges. A weak Megathermal event took place between 8.5 and 6.0 ka B.P., followed by Neoglacial events exhibiting peak cold at 5.3-4.7 ka, 3.1-1.5 ka, and the Little Ice Age （LIA） after 0.7 ka. Subsequently, mean annual air temperature has increased by 4 ℃.展开更多
基金supported by the Chinese National Basic Research Program(Grant Nos.2010CB950502 and 2012CB955202)the "Strategic Priority Research Program Climate Change:Carbon Budget and Relevant Issues" of the Chinese Academy of Sciences(Grant No.XDA05110301)+2 种基金the National Natural Science Foundation of China(Grant Nos.41006008 and 41023002)the public science and technology research funds projects of meteorology(Grant No.GYHY200906020)the National Key Technologies R&D Program project(Grant No.2010AA012302)
文摘Paleoclimate simulations of the mid-Holocene （MH） and Last Glacial maximum （LGM） by the latest versions of the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 and Grid-point Version 2 （FGOALS-s2 and g2） are evaluated in this study. The MH is characterized by changes of insolation induced by orbital parameters, and the LGM is a glacial period with large changes in greenhouse gases, sea level and ice sheets. For the MH, both versions of FGOALS simulate reasonable responses to the changes of insolation, such as the enhanced summer monsoon in African-Asian regions. Model differences can be identified at regional and seasonal scales. The global annual mean surface air temperature （TAS） shows no significant change in FGOALS-s2, while FGOALS-g2 shows a global cooling of about 0.7~C that is related with a strong cooling during boreal winter. The amplitude of ENSO is weaker in FGOALS-g2, which agrees with proxy data. For the LGM, FGOALS-g2 captures the features of the cold and dry glacial climate, including a global cooling of 4.6℃ and a decrease in precipitation by 10%. The ENSO is weaker at the LGM, with a tendency of stronger ENSO cold events. Sensitivity analysis shows that the Equilibrium Climate Sensitivity （ECS） estimated for FGOALS ranges between 4.23℃ and 4.59℃. The sensitivity of precipitation to the changes of TAS is -2.3%℃-1, which agrees with previous studies. FGOALS-g2 shows better simulations of the Atlantic Meridional Overturning Circulation （AMOC） and African summer monsoon precipitation in the MH when compared with FGOALS-gl.0; however, it is hard to conclude any improvements for the LGM.
基金This paper is supported by the Innovation Program of the Chi-nese Academy of Sciences (No. KZCX2-YW-211)the Na-tional Natural Science Foundation of China (No. 40676043)+1 种基金the Foundation of Key Laboratory of Marginal Sea Geology, the South China Sea Institute of Oceanology, Chinese Academy of Sciences (No. MSGL0509)the Start-up Foundation for Doctor Scientific Research of South China Sea Institute of Oceanology, Chinese Academy of Sciences
文摘In this article, Milkov and Sassen＇s model is selected to calculate the thickness of the gas hydrate stable zone （GHSZ） and the amount of gas hydrate in the Xisha （西沙） Trough at present and at the last glacial maximum （LGM）, respectively, and the effects of the changes in the bottom water temperature and the sea level on these were also discussed. The average thickness of the GHSZ in Xisha Trough is estimated to be 287 m and 299 m based on the relationship between the GHSZ thickness and the water depth established in this study at present and at LGM, respectively. Then, by assuming that the distributed area of gas hydrates is 8 000 km^2 and that the gas hydrate saturation is 1.2% of the sediment volume, the amounts of gas hydrate are estimated to be -2.76×10^10 m^3 and -2.87×10^10 m^3, and the volumes of hydrate-bound gases are -4.52×10^12 m^3 and -4.71×10^12 m^3 at present and at LGM, respectively. The above results show that the thickness of GHSZ decreases with the bottom water temperature increase and increases with the sea level increase, wherein the effect of the former is larger than that of the latter, that the average thickness of GHSZ in Xisha Trough had been reduced by -12 m, and that 1.9×10^11 m^3 of methane is released from approximately 1.1×10^9m^3 of gas hydrate since LGM. The released methane should have greatly affected the environment.
文摘The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This paper examines their effects on the current evidence for the timing of past glaciations, and the development and evolution of permafrost. There are two theories regarding glaciation on the Qinghai-Tibet Plateau （QTP）. Kuhle suggested that there was a major, unified ice-cap during the Last Glacial Maximum （LGM）, whereas major Chinese glaciologists and others have not found or verified reliable evidence for this per se. There have been limited glaciations during the last 1.1 Ma B.P. but with increasing dominance of permafrost including both primary and secondary tessellons infilled with rock, sand or loess. The East Asia Monsoon was absent in this area during the main LGM, starting at 〉30 ka B.P. on the plateau, with sufficient precipitation reappearing about 19 ka B.P. to produce ice-wedges. A weak Megathermal event took place between 8.5 and 6.0 ka B.P., followed by Neoglacial events exhibiting peak cold at 5.3-4.7 ka, 3.1-1.5 ka, and the Little Ice Age （LIA） after 0.7 ka. Subsequently, mean annual air temperature has increased by 4 ℃.
