Yilong lake level record documents coherent regional-scale changes in Holocene water balance in Yunnan, southwestern China

Abstract

Although Holocene-scale trends in Indian Summer Monsoon (ISM) variability have been well-established, manifestations and drivers of centennial- and multi-decadal-scale variability are still debated. Additionally, the extent to which proxies reflect abrupt climatic changes rather than proxy-specific thresholds is unclear. To address these questions, we summarize a 9200-year record from Yilong Lake in Yunnan China using multiple proxies including oxygen and carbon isotopes of authigenic calcite as well as Ti/Al ratio to characterize lake hydrologic balance and catchment erosion, respectively. We compare these results to two other well-studied nearby lakes on the Yunnan Plateau. At all three lakes, the Holocene-scale waning of the ISM is evident, but punctuated by abrupt shifts indicative of lower precipitation and/or greater evaporation at 7900, 5500, and 4500 cal yr B.P. We suggest that a shift to a positive mean-state of the Indian Ocean Dipole lasting multiple centuries can account for these events, with possible moderating influence from El Niño Southern Oscillation. After 1500 cal yr B.P., Yilong oxygen isotopes shift to less negative values as a result of human manipulation of hydrologic balance, coincident with the deposition of a red clay layer from catchment erosion. These results are similar to other Yunnan lakes although the intensity of anthropogenic management of Yilong's hydrologic balance is substantially smaller than at the other regional lakes. These results underscore the diversity of anthropogenic impacts to lakes, even ones that are only a few kilometers apart, and demonstrate spatiotemporal differences in freshwater resource use.