Arid and semi-arid zones are not only environmentally fragile but also the major source of global dust deposits and sandstorms. In the context of global warming, studies about the history of environmental changes in arid zones are crucial to predicting future trends as well. However, there has long been a paucity of paleoenvironmental records in arid zones. Moreover, relevant opinions have always been the subject of intense debate. LI Hongwei and YANG Xiaoping et al. at the Zhejiang University School of Earth Sciences, in collaboration with their peers based in China, the USA and Denmark, discovered paleolakes in the East Gobi Desert and reconstructed the hydrological and climatic conditions over the last 120,000 years. Their findings are published in the journal Nature Communications.
After years of fieldwork and laboratory analyses, the researchers discovered a series of evidence about the palaeohydrological landscapes, lacustrine and fluvial sediments and biological fossils in the northwestern margin of the Hunshandake Sandy Land and identified a large palaeohydrological network consisting of four former lakes. Using a combination of radiocarbon, uranium series and luminescence dating methods, they reconstructed two megalake systems over the last 120,000 years: Marine Isotope Stage 5 (about 80,000-120,000 years ago) and the mid-Holocene (about 6,000-7000 years ago). Paleolakes covered an area of 15,500km2 at their maximum extension during Marine Isotope Stage 5, the largest paleolake of the same period ever found in the Gobi Desert so far. The winter temperature during Marine Isotope Stage 5 was suggested to be 10°C higher than at present, and precipitation was likely to be as much as 2.2–2.5 times of modern values. During the mid-Holocene, the lake area was much smaller, but precipitation was shown to be still 1.8-2.1 times as much as today’s amount.
This work is of great value to understanding the current climate change too. In recent years, against the backdrop of Arctic warming, the mid-latitude area in the northern hemisphere has become considerably cold in winter during some years. Quite a few scholars attribute Arctic warming to the instability of the westerly jet, thereby inducing cold air to prevail in the mid-latitudes. However, this study indicates that the mid- and high-latitude areas may also become warmer in the years to come. This finding has important implications for the assessment of today’s global warming.