Evolution and changes of permafrost on the Qinghai-Tibet Plateau during the Late Quaternary

Abstract

Due to the uplift of Qinghai-Tibet Plateau (QTP), the cryosphere gradually developed on the higher mountain summits after the Neocene, becoming widespread during the Late Quaternary. During this time, permafrost on the QTP experienced repeated expansion and degradation. Based on the remains and cross-correlation with other proxy records such as those from glacial landforms, ice-core and paleogeography, the evolution and changes of permafrost and environmental changes on the QTP during the past 150, 000 years were deduced and are presented in this paper. At least four obvious cycles of the extensive and intensive development, expansion and decay of permafrost occurred during the periods of 150-130, 80-50, 30-14 and after 10.8 ka B.P.. During the Holocene, fluctuating climatic environments affected the permafrost on the QTP, and the peripheral mountains experienced six periods of discernible permafrost changes:(1) Stable development of permafrost in the early Holocene (10.8 to 8.5-7.0 ka B.P.); (2) Intensive permafrost degradation during the Holocene Megathermal Period (HMP, from 8.5-7.0 to 4.0-3.0 ka B.P.); (3) Permafrost expansion during the early Neoglacial period (ca. 4, 000-3, 000 to 1, 000 a B.P.); (4) Relative degradation during the Medieval Warm Period (MWP, from 1, 000 to 500 a B.P.); (5) Expansion of permafrost during the Little Ice Age (LIA, from 500 to 100 a B.P.); (6) Observed and predicted degradation of permafrost during the 20 th and 21 st century. Each period differed greatly in paleoclimate, paleoenvironment, and permafrost distribution, thickness, areal extent, and ground temperatures, as well as in the development of periglacial phenomena. Statistically, closer dating of the onset permafrost formation, more identification of permafrost remains with richer proxy information about paleoenvironment, and more dating information enable higher resolution for paleo-permafrost reconstruction. Based on the scenarios of persistent climate warming of 2.2~2.6℃ in the next 50 years, and in combination of the monitored trends of climate and permafrost changes, and model predictions suggest an accelerated regional degradation of plateau permafrost. Therefore, during the first half of the 21 st century, profound changes in the stability of alpine ecosystems and hydro (geo) logical environments in the source regions of the Yangtze and Yellow rivers may occur. The foundation stability of key engineering infrastructures and sustainable economic development in cold regions on the QTP may be affected.