In:
Progress in Physical Geography: Earth and Environment, SAGE Publications, Vol. 44, No. 4 ( 2020-08), p. 572-588
Abstract:
The scarcity of modern process studies of the relationship between climatic variables and lake-water oxygen isotope (δ 18 O LW ) composition has restricted our understanding of the climatic significance of oxygen isotope (δ 18 O) records from lake sediments. We measured changes in δ 18 O LW at four lakes (Nanyihu, Gonghai, Mayinghai and Xihaizi) at various locations across the East Asian summer monsoon (EASM) region, from December 2016 to January 2018. The variations in δ 18 O LW at Lake Nanyihu, located in the lower reach of the Yangtze River, are controlled by precipitation oxygen isotope (δ 18 O P ) composition, temperature and evaporation during the non-monsoon season. However, the variations in δ 18 O LW at the lakes close to the northern limit of the EASM (Gonghai, Mayinghai and Xihaizi) are affected not only by δ 18 O P , temperature and evaporation, but also by the replenishment of groundwater during the non-monsoon season. In general, during the non-monsoon season, the variation of δ 18 O LW exhibits a variety of patterns and the controlling factors across the EASM region are complex. During the monsoon season, although the effect of evaporation-induced isotopic enrichment still affects δ 18 O LW , the variations in δ 18 O LW are more influenced by the supply of abundant precipitation with lower δ 18 O P to the lakes, which caused a substantial decrease in δ 18 O LW across the EASM region in this season. Therefore, the variations in δ 18 O LW mainly reflect the δ 18 O P of the EASM during the monsoon season. However, the timing of the peak in monsoon precipitation does not correspond well to minima in δ 18 O LW , and correlation analysis reveals that there is only a weak relationship between δ 18 O LW and precipitation/humidity at all four lakes during the monsoon season. These findings demonstrate that although δ 18 O LW can represent the δ 18 O P of the EASM, it does not reflect precipitation/humidity during the monsoon season. Overall, our findings indicate that the seasonal variations of δ 18 O LW across the EASM region are controlled by different climatic variables, which implies that the interpretation of lacustrine δ 18 O records across the EASM region as an indicator of regional effective precipitation/humidity needs to be reassessed.
Type of Medium:
Online Resource
ISSN:
0309-1333
,
1477-0296
DOI:
10.1177/0309133319896338
Language:
English
Publisher:
SAGE Publications
Publication Date:
2020
detail.hit.zdb_id:
131848-2
detail.hit.zdb_id:
2006623-5
SSG:
14
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