近30年来青藏高原西大滩多年冻土变化

Permafrost Changes in the Northern Limit of Permafrost on the Qinghai-Tibet Plateau in the Last 30 Years

结合1975年已有勘探资料,对青藏高原多年冻土北界西大滩进行了雷达勘探。勘探发现,近30年来青藏高原多年冻土北界发生较大规模的多年冻土退化,多年冻土面积从1975年的160.5 km2退化成现在的141.0 km2,缩小约12%;开始出现多年冻土的最低高程为4 385 m,比1975年升高了25 m。近30年来研究区的气候变化是造成北界多年冻土退化的主要原因。相同气候背景下,多年冻土腹部地温有升高,但在30年尺度上不会发生明显的退化。本次冻土区域调查的结果可为检验冻土-气候关系模型的可靠与否提供依据。

A radar survey on permafrost changes has been conducted in Xidatan, the northern limit of permafrost on the Qinghai-Tibet Plateau (QTP). Comparison with the survey result of 1975 in the same region shows that, in the last 30 years, permafrost degradation has occurred on a relatively large scale in the northern limit of permafrost on the QTP. Permafrost area in the region of interest has been shrunk to 141.0 km 2 from original 160.5 km 2 in 1975, or permafrost reduction rate estimated being about 12%. The lowest altitude with permafrost coverage is 4385 m exposed in this survey, 25 m higher than that of 1975. Climate change during the past 3 decades in the permafrost northern limit mostly contributes to the reduction. However, under the same climate scenario, no significant degradation was found in the scale of 30 years in the continuous permafrost zone, despite distinct ground temperature rising there. The survey result shows a fact to tell how and how much permafrost responses to climate change, and provides a reference to identify interaction models between permafrost and climate system.