Abstract
Lake-level reconstruction of inland enclosed lakes especially for monsoon-sensitive areas is of great significance to reveal regional climate changes. Daihai, a typical enclosed lake at the marginal of the East Asian summer monsoon (EASM) area in north China, is sensitive to climate changes due to its unique regional characteristics. There were a series of lakeshore terraces, highstand lacustrine sediments, and braided river deltas, providing sufficient geomorphologic and stratigraphic evidence for the reconstruction of lake-level fluctuations of Daihai. Reconstructed lake-level variations during the early and mid-Holocene were constructed based on 22 quartz optical stimulated luminescence (OSL) ages from six well-preserved profiles around Daihai Basin. Our results indicated Daihai showed a relatively low level at 10.2 ka, and a gradually increasing lake level following the enhanced monsoon precipitation during the mid-Holocene. Specifically, the high lake level began to develop at 8.1 ka and reached the maximum at 5.2 ka, with ∼40 m higher than present. At this time, the lake area expanded to ∼400 km2, approximately six times as large as that of present, corresponding to the maximum monsoon precipitation and intensity of EASM during the mid-Holocene. However, our stratigraphic records showed a part of the depositional records in the north and east of the Daihai was missed after 5.2 ka, probably indicating a sudden drop of the Daihai lake level. These rapid level fluctuations were likely to be interpreted by some local scenarios and need to be further investigated in the future. Overall, the lake-level fluctuation of Daihai during the early and mid-Holocene was slightly different from that observed in the previously published regional records. Possibly, the interaction of the EASM and regional feedback from topography, and hydrology factors might have contributed to the spatial complexity and distinction.
Highlights
Exploring the evidence of the past global climate change in environment-sensitive regions and obtaining its underlying mechanisms are of great significance for the scientific prediction of future climate change (International GeosphereBiosphere Programme, IGBP)
Our results showed that the high lake level developed at 5.2 ka, and a sudden declined level occurred after 5.2 ka, while reconstruction results in Figure 7B indicated Daihai expanded on a large scale with the abundant monsoon effective precipitation and humid climate at 8.1 Cal ka B.P (7.3 ka B.P), and this persistent and stable high lake-level stage remained until 3.4 Cal ka B.P (3.2 ka B.P) (Sun et al, 2009)
A series of lakeshore terraces with different heights and braided river deltas around Daihai providing direct geomorphic evidence were used to reconstruct the history of lake-level fluctuations based on the optical stimulated luminescence (OSL) dating method during the early and mid-Holocene
Summary
Exploring the evidence of the past global climate change in environment-sensitive regions and obtaining its underlying mechanisms are of great significance for the scientific prediction of future climate change (International GeosphereBiosphere Programme, IGBP). There are large numbers of inland enclosed lakes near the East Asian monsoon margin of China which are highly sensitive to climate change due to its unique regional characteristics. Their lake-level fluctuations are the most direct indicators of regional precipitation and moisture variability related to the intensity of monsoon activities and climate change (Liu et al, 2015; Li et al, 2020a). The unique characteristics of the interlaced nomadic with agricultural civilization make it the most sensitive and typical region responding to global climate change. Daihai is a typical inland enclosed lake in Inner Mongolia, whose lake-level fluctuations are of great significance to indicate the regional climate change. There are still many discrepancies and arguments, even conflicts with regard to climate change patterns among them, especially on the timing of highstand records
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