The impact of latitude and altitude on the extent of permafrost during the Last Permafrost Maximum (LPM) in North China

摘要

This paper examines the relationship between the extent of permafrost during the Last Permafrost Maximum (LPM, largely between 22 and 17 ka BP) and the altitudinal and latitudinal temperature gradients that controlled its extent. The region chosen, namely, the Qinghai-Tibet Plateau and the transition to the northern adjacent plains in the North China Plain, is of relatively limited extent in order to avoid regional effects. This area extends over 15 degrees of latitude while altitudes vary from 1000 to 1500 m above sealevel (asl) in the northern plains to more than 4000m asl in the central-to-south part of the Qinghai-Tibet Plateau. The respective lowest southernmost permafrost occurrences at a northern and a southern position are used for reconstruction of the latitudinal and altitudinal gradients.As a first approximation, we conclude that the elevation compensation during the LPM for a 1 degrees latitude change was between 309 m and 385 m. This is considerably higher than the value calculated for existing permafrost in the region that uses thermal data at a depth of zero amplitude change (139-198 m altitudinal compensation for 1 degrees latitude). (C) 2019 Elsevier B.V. All rights reserved.