摘要
根据青藏高原及其它地区的降温证据和降温条件下的环境变化模拟，讨论了青藏高原冰期环境变化及机制问题。从模拟结果看，在７～９℃降温条件下，高原冰雪带面积可占高原面积的１／５到１／２。考虑到降温条件下雪盖反射引起的高原冷却所起的正反馈作用，冰期高原上并不排除从山谷冰川发育较大冰盖的可能性。不管冰期高原上有无大面积的冰盖，青藏高原冰期环境出现大的变化是无疑问的。这种变化对冰期季风变化乃至全球气候变化的影响可能是深刻的。
ecent studies from Greenland suggested a temperature drop of 20~21℃ duringthe LGM (last glacial maximum) and a drop of 14± 30℃ during the YD (YoungerDryas) event. Studies in North America also revealed that a drop of 16℃ intemperature for the last glacial Period. In the tropics, more and more evidence hasdemonstrated that the changes in temperature between glacial and interglacial periodscan be as great as 4~5℃. These results are significantly different from previousunderstanding. It is, therefore, necessary to re-evaluate the glacial environment ofQinghai-Xizang Plateau.In the LGM, data from tropic and sub-tropic mountains demonstrated that theELAs (equilibrium line altitudes) had depressed by 900~ 1000m in altitude. In theQinghai-Xizang Plateau, evidence from oxygen isotope ratio in ice and from pollenrecords also suggested that the temperature has dropped by 7~9℃, corresponding toa depression of 1000m in ELA, during glacial Period. The records of lake level onand surrounding the plateau indicated a sustained moisture supply to the plateauduring glacial Periods. With these estimates, a new model developed by the author(Zhang Xinshi) has conducted and displayed that a great part of the plateau might becovered by snow and glaciers (nival ) with a temperature decrease of about 5~9℃.Meanwhile,considering that the snow covers may play a positive feedback in loweringtemperature over the plateau, we are convinced that the plateau has the possibility toform glaciers in great extent or local dispersed ice sheets during glacial Periods.It is quite evident that the environment of the plateau during glacial Period haschanged significantly with a great increase in surface albedo. The increase and theabrupt fluctuations in the surface albedo may play an important role in the Asianmonsoon oscillations and the subsequent fluctuations in global atmospheric watervapour, which, in turn, may remarkably influence the global climate.
出处
《第四纪研究》
CAS
CSCD
北大核心
1999年第5期385-396,T004,共13页
Quaternary Sciences
基金
国家重点基础研究专项经费
中国科学院青藏高原研究项目
国家自然科学基金
