Glacial activity reflected in a continuous lacustrine record since the early Holocene from the proglacial Laigu Lake on the southeastern Tibetan Plateau

Abstract

The southeastern Tibetan Plateau is an important area of monsoonal maritime glaciation, and it serves as a watershed for several major Asian rivers, including the Brahmaputra River and the Lantsang River. Glacial activity is sensitive to climate change in this area. However, due to high annual ablation and accumulation in this region, ice cores over long time scales are difficult to retrieve. In addition, reconstructed glacial activity from moraine dates is usually discontinuous. Here, we use a sediment core retrieved from Laigu Lake, which is a proglacial lake located in the headwaters of the Parlung Zangbo River, the largest tributary of the Brahmaputra River, to reflect glacial activities over the last ~8000years in this area. Samples of the sediment core were analyzed for magnetic susceptibility, XRF (X-ray florescence) scanned elemental concentration and grain size. The results indicated that the magnetic susceptibility and CPS (peak area counts per second) of strontium (Sr) could be used as proxies for glacial activity. The CPS of Sr and the magnetic susceptibility were lower and the glacial activity was weak before 4.3calka BP. Expansion of the glaciers in this area began from 4.3calka BP and continued to develop after ~3.3calka BP. From 2.2calka BP to 1.6calka BP, the glaciers retreated substantially, followed by another development period until the onset of modern global warming. Based on our findings and other climate records, we concluded that glacial activity in the southeastern Tibetan Plateau areas was mainly influenced by Northern Hemisphere temperatures and summer insolation over a sub-orbital time scale, but did not respond to the Indian monsoon.