胡镕
南京大学地理与海洋科学学院, 江苏 南京 210023

基金项目: 中国博士后科学基金项目（批准号：2017M620201）和国家重点研究发展计划——全球变化及应对项目（批准号：2016YFA0600503）共同资助


详细信息

作者简介: 胡镕, 女, 30岁, 博士后, 表生地球化学和全球变化研究, E-mail:ronghu@nju.edu.cn

中图分类号: P725.1;Q915.811⁺.1;P597⁺.2;P534.63

收稿日期:2018-06-17
修回日期:2018-08-09
刊出日期:2018-09-30

A comparative study of benthic foraminifera oxygen isotopes in the North Atlantic during Holocene and MIS 5e

Hu Rong
School of Geography and Ocean Science, Nanjing University, Nanjing 210023, Jiangsu



MSC: P725.1;Q915.811⁺.1;P597⁺.2;P534.63

--> Received Date: 17 June 2018
Revised Date: 09 August 2018
Publish Date: 30 September 2018


摘要
摘要:北大西洋（特别是亚极地海区）是对全球气候变化响应最敏感的区域之一，也是全球气候变化研究关注的焦点之一。地质记录和模拟研究指出末次间冰期（MIS 5e）全球地表平均温度比全新世（Holocene）高约1℃，因而可以作为未来全球变暖趋势的历史对照，但目前北大西洋水体温盐变化在这两个时期的对比研究仍然较少。底栖有孔虫氧同位素作为古气候研究常用的指标，与冰量、温度和洋流变化紧密相关。本文统计并对比了北大西洋47个深海沉积物钻孔MIS 5e和全新世的底栖有孔虫氧同位素数据，发现研究区不同深度、不同纬度的数据在这两个间冰期具有系统的差异。MIS 5e氧同位素平均值和极低值比全新世系统性偏轻0.08 ‰，反映了陆地冰量变化对整个区域的影响，且深水温度整体可能比全新世偏高。氧同位素时空分布表明北大西洋中层水（1~2 km）全新世和MIS 5e的有孔虫氧同位素差值（> 0.2 ‰）比深水（> 2 km）更显著，可能记录更大的温度变化幅度，而1.5 km之上MIS 5e氧同位素值变重（平均重约0.36 ‰）则主要响应了大洋环流的变化。此外，高纬地区（45°N以北）深水底栖有孔虫氧同位素值在MIS 5e系统性偏轻约0.12 ‰，比中低纬（0°~45°N）深水变化更显著，可能反映高纬深水变暖程度更高，与海表温度重建和模拟结果相吻合。因此，联合多钻孔的底栖有孔虫氧同位素是分辨区域古海洋变化的有效手段，在未来气候变暖中北大西洋高纬和中层海域的变化是气候模式需要重点关注的区域之一。
关键词: 北大西洋/
底栖有孔虫/
氧同位素/
末次间冰期/
全新世

Abstract:The North Atlantic plays an important role in the global climate system and its link with climate change has received much attention. Marine Isotope Stage(MIS) 5e with a warmer climate than the Holocene is considered as an analogy for future warming climate. To date, there are few deepwater temperature and salinity comparisons between these two recent interglacial periods in the North Atlantic. Benthic foraminifera oxygen isotope(δ¹⁸O) has long been analysed in paleoclimate studies since its variation closely related to global ice volume, temperature and ocean circulation changes. In this study, a comparison of benthic foraminifera oxygen isotope during the Holocene(0~12 ka) and MIS 5e(116~130 ka) stages from 47 deep-sea sediment cores in the North Atlantic is presented to investigate whether a systematic δ¹⁸O difference exists during the last two interglacial periods. This database suggests the δ¹⁸O signatures during the MIS 5e were systematically lighter(ca. 0.08 ‰) than those in the Holocene, indicating potential reduced global continent ice volume and/or warmer deep-sea temperature in the North Atlantic. Although the δ¹⁸O differences between Holocene and MIS 5e are small, the systematical trends in our database confirmed by t-test provide confidence in our proposal that the different climate signals are observed by the δ¹⁸O comparison. This study further examines the contribution of sea level or temperature changes in the MIS 5e and Holocene δ¹⁸O differences tentatively based on the empirical relationships between δ¹⁸O and sea level/temperature in the palaeoceanography field, which suggests a dominant control of higher sea level and a slight warmer North Atlantic deepwater in the MIS 5e. A further regional examination of δ¹⁸O difference between Holocene and MIS 5e shows larger temporal variations in the intermediate depth cores between 1 and 2 km water depths (> 0.2 ‰) than cores below, implying enlarged magnitude of temperature changes, and the heavier δ¹⁸O of cores above 1.5 km during the MIS 5e averaged by ca.0.36 ‰ might be associated with regional ocean circulation changes. Moreover, the decrease of ca.0.12 ‰ in MIS 5e benthic foraminifera δ¹⁸O of high latitude deep cores(> 45°N) is more pronounced than that of low-middle latitude deep cores(0°~45°N), inferring a more significant warming in the high latitude deep water, which is in accordance with sea surface temperature reconstructions and modelling results. Benthic oxygen isotope investigation based on multiple sediment cores is a useful approach to identify regional changes in oceanographic changes. Changes in regions such as the high latitude and intermediate depth North Atlantic would deserve special attention in future climate simulations.
Key words:North Atlantic/
benthic foraminifera/
oxygen isotope/
MIS 5e/
Holocene



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