第四纪中期青藏高原冰冻圈的演化及其与全球变化的联系

Evolution of the Cryosphere in the Tibetan Plateau, China, and its Relationship with the Global Change in the Mid Quaternary

文章给出了冰冻圈的含义与组成，新生代４２Ｍａ前南极冰盖出现至中更新世，是地球上冰冻圈发展的漫长过程青藏高原在早更新世只在个别高峰有冰川作用，直到１１～０６ＭａＢＰ的昆（仑）黄（河）运动，将高原面抬升至３５００ｍ左右高度的降温作用和同时期地球接受日射的轨道转型（由４１万年周期的轨道倾斜率过渡为１０万年周期的轨道偏心率控制）及相伴的降温作用相耦合，形成了测年数据在０６～０８ＭａＢＰ间的倒数第三次冰期或最大冰期冰川规模最大时相当于ＭＩＳ１６阶段，冰川面积在５×１０５ｋｍ２以上，其时冰川平衡线处夏季气温１～２℃，高于现代冰川，降水量在中东部４个山区为现代的１８～３２倍，在干旱的西昆仑山仅较现代多３０％高原西部有大规模的多年冻土发育，除夏季外，高原存在厚度不等的稳定积雪反射率大幅度提高与积雪融化耗热，导致高原从以前的热源作用转变成多数月份起冷源作用，使地面温度进一步降低，加强高原外吹的冬季风，减弱了夏季的西南季风降水但高原中东部受稳定的南支西风急流与夏季热低压影响，降水仍然较丰富，形成湿冷气候，这对高原本身和四周地区都有重要的影响位于倒数第三次冰期与倒数第二次冰期间的间冰期可以ＭＩＳ１３阶段?

This paper defines the implication and composition of the cryosphere and presents the process of the cryospheric evolution in a very long period from the appearance of ice cover in Antarctic about 42 Ma ago to the mid Pleistocene During the early Pleistocene, there were only a few peaks of glaciation occurred in the Himalayas Until the orogenic movement of Kun-huang from 1 1 to 0 6 Ma BP, the plateau ground lifted up to about 3 500 m, resulting in the plateau's cooling; and at the same time, the control of the earth orbit taking in solar insolation changed from the orbital incline rate of 41 ka in a cycle to the eccentricity of 100 ka in a cycle, concomitantly resulting in the Plateau's cooling as well Because the events mentioned above were coupled, the third glaciation from the last or the maximum glaciation occurred in 0 6 to 0 8 Ma BP The period when the maximum glaciation occurred was comparable with MIS16 Period, with the total glacier area more than 5×10 5 km 2 Air temperature in summer at the equilibrium line of glaciers was 1～2℃ higher than that at present Precipitation in four mountainous areas of the mid and east plateau was 1 8～3 2 times as much as that at present, while precipitation in the arid West Kunlun Mountains was only 30% more than the present one Permafrost grew at a large scale in the west plateau and stable snow cover existed with different depths in the plateau, except for summer Consequently, the albedo was greatly increased on one hand and the snow melting consumed a large amount of heat energy on the other hand, resulting in the plateau's effect changing from a heat source of a year-round to a cold source of most months in a year and furthermore resulting in a decrease in air temperature The winter monsoon to the outside was enhanced and as a result, summer precipitation from the southwest monsoon decreased However, precipitation was still rich and climate was relatively cool and humid in the mid and east plateau where climate constantly affected by the south branch of the west jet stream and by the hot low in summer, which in turn had an important impact on climate of the plateau itself and its nearby areas The interglacial between the last but one and the last but two glaciations was symbolized by MIS13 period During the interglacial, climate was much warmer than that in glaciation Forestry was distributed near what is now called Qinghai-Xizang Highway and the laterite crust of weathering grew in the south plateau The plateau's role as a heat source was strengthened, resulting in an enhancement of summer monsoon Except for existence of a small number of high-elevation glaciers, such as the Guliya Glacier, a large part of glaciers and permafrost areas might be fully depleted and disappeared