Late Holocene monsoon climate of northeastern Taiwan inferred from elemental (C, N) and isotopic (未¹³C, 未¹⁵N) data in lake sediments

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• 作者：Kandasamy Selvaraj^a ; ^b ; ^{selvaraj@xmu.edu.cn} ; ^{kselva8@yahoo.com} ; Kuo-Yen Wei^c ; Kon-Kee Liu^d ; Shuh-Ji Kao^a ; ^b
• 关键词：Total organic carbon ; C/N ratio ; Stable isotopes ; East Asian monsoon ; Late Holocene ; Emerald Peak Lake ; Subtropical Taiwan
• 刊名：Quaternary Science Reviews
• 出版年：2012
• 期刊代码：78_02773791
• 类别：ear
• 出版时间：22 March, 2012
• 卷：37
• 期：Complete
• 页码：48-60
• 文件大小：1406 K

摘要

Little information exists about centennial-scale climate variability on oceanic islands in the western Pacific where the East Asian monsoon (EAM) strongly influences the climate, mountain ecosystem and the society. In this study, we investigate a 168聽cm long sediment core recovered from Emerald Peak Lake in subalpine NE Taiwan for the contents of grain size, total organic carbon (TOC), C/N ratio, and stable isotopes (未¹³C and 未¹⁵N) to reconstruct the monsoon climate and vegetation density during the late Holocene. Six radiocarbon (¹⁴C) ages obtained on plant remains used for the chronology indicate that the sediment core has been accumulated since 鈭?770聽cal BP with a mean sedimentation rate of 44.6 cm/ka. The sub-centennial resolution of our proxy records reveals strong fluctuations of the EAM and vegetation density for the past 鈭?770聽cal BP. The greater contents of coarse and medium sediments with overall decreasing trends from 3770 to 2000聽cal BP suggest an increasing fine sediment influx from the catchment likely due to an increasing lake water level. Although low TOC content, C/N ratio, and enriched 未¹³C values in bulk and fine sediments during this interval suggest a sparsely vegetated catchment, increasing trends of TOC content and C/N ratio together with decreasing trends of 未¹³C and 未¹⁵N values indicate a strengthening pattern of summer monsoon. This is in contrast to a decreasing monsoon strength inferred from Dongge Cave 未¹⁸O record at that time, supporting the idea of anti-phasing of summer EAM and Indian summer monsoon. Since 2000聽cal BP, higher content of fine sediments with high TOC content and C/N ratio but relatively depleted 未¹³C and low 未¹⁵N values suggest a high but stable lake water level and dense C3 plants, consistent with a stronger summer monsoon in a wet climate. Within this general trend, we interpret a prominent change of proxy parameters in sediments from聽鈭?60 to 150聽cal BP, as subtropical evidence for the Little Ice Age in NE Taiwan. By comparing our proxy records with other diverse land and marine records from southern China and adjoining marine realm, we demonstrate that the centennial to millennial-scale fluctuations of the summer EAM over the northeastern Taiwan during the late Holocene have been largely modulated by the tropical Pacific forcing through El Ni帽o along with solar forcing.