Snow accumulation variability at altitude of 7010 m a.s.l. in Muztag Ata Mountain in Pamir Plateau during 1958-2002

摘要

Precipitation over high mountain is significant for glacier development and river runoff in arid Tarim Basin in the northwest China. However, a coherent perspective of precipitation variability at high-altitude in Tarim Basin has not been presented until now. Here, a 41-m ice core at altitude of 7010 m a.s.l. was drilled and gotten to determine annual snow accumulation rates at Muztag Ata Mountain in the headwater of Tarim River in Pamir Plateau during summer 2003. Using strong seasonally variation of oxygen isotope and beta-radioactivity reference layers, the core was dated reliably back to 1958 and resulted in a 45-year record between 1958 and 2002. The mean annual snow accumulation was about 605 mm water equivalent, which is almost 10 times than precipitation in piedmont with elevation below 3000 m a.s.l. The snow accumulation is characterized by high values in 1960s and early 1970s, followed by a drop in the middle 1970s and a recent decreasing trend. Further analysis suggests the upstream zonal flow variation as the major mechanism linking the regional snow accumulation fluctuation to macroscale circulation conditions. During the high snow accumulation years, the westerly winds between 30 and 50 degrees N from the Mediterranean Sea to Pamir Plateau are weakened. The decreased upstream westerly winds generate anomalous cyclonic flows in the Pamir Plateau, which results in an enhanced advection of moisture from the tropics to the vicinity of Muztag Ata Mountain and is thus consistent with enhanced snow accumulation at the core site. During the low snow accumulation years, the above processes are reversed. On the basis of this high-altitude snow accumulation and temperature, a linear regression model is established to simulate annual mass balance in Muztag Ata region. Results reveal that snow accumulation conditions largely determine the annual mass-balance, which has stronger impaction on Tarim River runoff. (C) 2015 Elsevier B.V. All rights reserved.