长江-黄河源区未来气候情景下的生态环境变化

在IPCC的情景下,青藏高原到2100年气温将上升2～3.6℃,最大的升温将出现在冬季,降水模式将会逐渐发生改变,从北部的增加到西南的减少.对于江河源区的范围,到2100年增温在2.4～3.2℃,降水量增加约-50～200mm.植被群落在气候变化条件将发生明显变化,温带草原到寒温带针叶林群落的面积增加,而温带荒漠到冰缘荒漠的面积都缩小,分布界线向更高的海拔高度迁移.到2100年气温上升3℃,降水不变则冰川长度小于4km以下的冰川大都消失,整个长江源区的冰川面积将减少约60%以上.如果考虑降水增加,冰川面积在2100年气候条件下减少约40%,将从现在的1168.18km²减少到00km²左右,冰川融水的比重也将会由现在的占河流总径流的25%下降到18%.另外,由于冰川大量退缩,草地和湿地蒸发量加大,许多湖泊将会退缩和干涸,沼泽地退化、沙化扩展,草地退化等一系列严重的生态问题将更加突出.

The Impact of Future Climate Change on Ecology and Environments in the Changjiang-Yellow Rivers Source Region

Mountain environments are essential to the survival of the global ecosystem. Mountains provide a large variety of both ecological and physical indicators, whose combined use might serve as a unique chance to observe and detect signals of global environmental change. The Changjiang-Yellow Rivers source region is an important ecological function area for the Qinghai-Tibetan Plateau, and also serious vulnerary for environment. Climate change during 20th century has significantly affected the cryosphere. Under climate scenarios, temperature of the Tibetan Plateau may rise by 2.5～3.6℃ by 2100 or so as compared to that at the end of the 20th century. Permafrost zone will greatly change after climate warming. Their area is expected to decrease and permafrost zone will be moving upward and degrading. The area of extreme stable zone will shrink from 5.59% at present to 0.65% in 2099, stable zone from 16.32% in present to 3.28% in 2099, and substable zone from 25.5% in present to 17.43% in 2099. Area will increase with air temperature rising for transition zone and unstable zone. Area of transition zone will change from 22.85% at present to 31.01% in 2099 and that of unstable zone from 10.8% at present to 27.46% in 2099. Extreme stable zone will transform into stable zone, stable zone into substable zone, substable zone into transition zone, transition zone into unstable zone and unstable zone will be in the stage of degradation. Air temperature rising results in changing of distribution of seasonal snow cover and regime of snowmelt runoff, snowfall increasing due to air temperature rising reaches 7%～10%,the snowmelt period stretches with the shifted advance 10 days. While the discharge increases, the peak of runoff also advances to May. For a warming rate of 0.03 K ·a^-1, without increase in precipitation, almost all less 4 km of glacier length would disappeared and 40% of all glaciers area here would survive until 2100. On the other hand, if the warming rate were to be limited to 0.03 K·a^-1 with an increase in precipitation of 10% per degree warming, the effect of a precipitation change of this magnitude is significant, but by no means enough to compensate for the enhanced melting due to the temperature rise, we predict that overall loss would be restricted to 40% of the 1990 area; the total area of glaciers would decreased from 1168.18 km² at present day to 700 km² until 2001 in the source region of Changjiang River. The area and volume of the glacier will greatly decrease, which will have great impact on the ecological environment of the source region of the Changjiang River. Climate change will affect the water balance, and particularly the amount of runoff and recharge, which in turn determines the water resources available for human and ecosystem uses.