Plio-Pleistocene Paleoclimate and Paleoelevation in the Northern Tibetan Plateau: Implications for the Establishment of Alpine permafrost and its stability during global climate change

Abstract:

The modern Tibetan Plateau represents a vast alpine ecosystem that is dominated by permafrost soils. Understanding the paleoelevation and paleoclimate history of the Plateau provides insight into the timing of establishment of permafrost. Viewed in the context of global cooling, we evaluate the extent to which alpine permafrost ecosystems will be lost associated with modern global change. In this study, we compare recently generated records of lake water composition, paleotemperature, and paleo-productivity from stable isotopes, clumped C-O isotopes, and other proxies from Lake Qinghai Basin and the Kunlun Pass Basis spanning from ~5 to 2 Ma and ~4.3 to ~1 Ma, respectively. Clumped isotope-based paleotemperatures in the Lake Qinghai Basin (3260 m) suggest that mean annual air temperature (MAAT) declined from ~4.4°C ± 3.6°C between 4.9 and 3.7 Ma to ~1.6°C ± 3.7°C between 3.3 and 2.1 Ma (decrease of 2.8 ± 5.1˚C). MAAT remained above 0°C, indicating that this region has not experienced sustained permafrost over this time period. Furthermore, the minor change in long term temperature suggests minimal changes in paleoelevation of <1000 m. In Kunlun Pass Basin (4600 m), clumped isotope-based paleotemperatures indicate ~8.0 °C cooling in this region at ~2.7-2.6 Ma, with warmer MAAT of ~1.2 ± 2°C in the Pliocene, indicating a transition to sustained permafrost conditions during the intensification of northern hemisphere glaciation. In this discussion, we explore the relationship between these records and its implications for changes in regional paleoelevation. We also discuss the sensitivity of alpine permafrost loss versus arctic permafrost loss to current warming trends.