近40a来中国喜马拉雅山不同流域冰湖演化特征

基于1970年代、1990、2000、2010年4个时相的冰湖编目数据,分析近40 a来中国喜马拉雅山区不同时段、不同流域和不同海拔冰湖的变化特征。近40 a来中国喜马拉雅山区冰湖变化总体呈现"数量弱减少、面积持续显著增大"的趋势,平均数量减少0.3%,面积增加53.1%±11.5%,但冰湖变化年代际差异明显。西部流域冰湖面积增速明显快于东部流域,由西至东,平均以线性递减率为2.4%/(°)的趋势减少。不同海拔高度的冰湖面积呈扩张态势,76.7%的流域冰湖面积年净增率在不同高度带上呈现出"单峰型"增长模式,其他流域呈"双峰型"甚至"多峰型"扩张模式,体现不同高程上冰湖扩张的复杂性与气候变化的垂直差异性。

Changes of Glacial Lakes in DifferentWatersheds of Chinese Himalaya during the Last Four Decades

Characteristics of glacial lake variation were analyzed in the views of temporal and spatial evolution based on four phases of glacier lake inventories of 1970s, 1990, 2000 and 2010 respectively. The glacier lake variations are characterized by a general trend of "weak decrease in the number and marked increase in the area" in Chinese Himalayas during the past 40 years. The number of glacier lakes decreased with a rate of 0.3%, and the area of glacier lakes increased with a rate of 53.1%±11.5%. The interdecadal differences are obvious, and 2000 is a turning point in the number of glacier lakes (the number of glacier lakes decreased before around the year of 2000, while increased after that), but the area of glacial lakes kept continuous growth in last 40 years. It was found that the growth rate of glacier lakes was much faster at western watersheds than that in the eastern watersheds and decreased with a linear rate of 2.4%/(°) from west to east. In addition, the glacial lake areas are widely expanding at different elevations. Therein, the annual net glacier lakes growth rate of 76.7% watersheds present a " single-peak " growth model at different elevations with 100 m bandwidth, and the others present "double-peak" or even " multi-peak " expanding models, which reflects the complexity of glacier lakes evolution at different elevations and the vertical differentiation of the climatic change. The positive correlation relationship is remarkable between the normalized glacier areas and the normalized glacier lake areas, and it appeared a trend of "normalized glacier areas decrease and normalized glacial lake areas increase" in different watersheds of Chinese Himalayas during the past 40 years.