刘天昊^1,2,,
常凤鸣^1,3,4,,,
李铁刚^2,4,5,,,
孙晗杰^1,3,4,
崔亦鹍^1,2,
王佳^1,2,
钱芳^1,2
1. 中国科学院海洋研究所海洋地质与环境重点实验室, 山东 青岛 266071
2. 中国科学院大学, 北京 100049
3. 中国科学院海洋大科学研究中心, 山东 青岛 266071
4. 青岛海洋科学与技术试点国家实验室, 海洋地质过程与环境功能实验室, 山东 青岛 266237
5. 自然资源部第一海洋研究所, 海洋沉积与环境地质重点实验室, 山东 青岛 266061

基金项目: 国家自然科学基金项目（批准号：41830539、41476041、41876041和41706040）、自然资源部"全球变化与海气相互作用"专项项目（批准号：GASI-GEOGE-04和GASI-GEOGE-06-02）、自然资源部第一海洋研究所海洋沉积与环境地质重点实验室开放基金项目（批准号：MASEG201901）和山东省"泰山****"建设工程专项经费项目（批准号：TSQN20182117）共同资助


详细信息

作者简介: 刘天昊, 男, 25岁, 硕士研究生, 古海洋与古环境研究, E-mail:liutianhao17@mails.ucas.ac.cn

通讯作者: 常凤鸣, E-mail:chfm@qdio.ac.cn; 李铁刚, E-mail:tgli@fio.org.cn

中图分类号: P721;P532

收稿日期:2019-11-16
修回日期:2020-02-15
刊出日期:2020-05-30

ENSO-like state in the tropical Pacific Ocean during the cold and warm periods of the galcial cycle since 450 ka

Liu Tianhao^1,2,,
Chang Fengming^1,3,4,,,
Li Tiegang^2,4,5,,,
Sun Hanjie^1,3,4,
Cui Yikun^1,2,
Wang Jia^1,2,
Qian Fang^1,2
1. Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, Shandong
2. University of Chinese Academy of Sciences, Beijing 100049
3. Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, Shandong
4. Laboratory for Marine Geology, Pilot National Laboratory for Marine Science and Technology(Qingdao), Qingdao 266237, Shandong
5. Key Laboratory of Marine Sedimentology and Environment Geology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, Shandong


More Information

Corresponding authors: Chang Fengming,E-mail:chfm@qdio.ac.cn ; Li Tiegang,E-mail:tgli@fio.org.cn

MSC: P721;P532

--> Received Date: 16 November 2019
Revised Date: 15 February 2020
Publish Date: 30 May 2020


摘要
摘要:作为现代最强的年际气候异常信号，厄尔尼诺-南方涛动（El Ni?o-Southern Oscillation，简称ENSO）过程对全球气候和海洋环境有显著影响。在长时间尺度上，低纬太平洋类ENSO式的热状态转变在古气候演化中也可能起了重要作用。目前对冰期旋回中热带太平洋类ENSO状态的研究多限于末次冰期，且据不同指标得出的认识存在着显著的差异。本文通过对IODP363航次U1486孔沉积物中浮游有孔虫Trilobatus sacculifer壳体的δ¹⁸O和Mg/Ca分析，重建了西太平洋暖池（Western Pacific Warm Pool，简称WPWP）核心区450 ka以来的表层海水温度（Sea Surface Temperature，简称SST）。结果显示近5次冰期旋回中WPWP核心区SST的波动范围为25.3~30.8 ℃，重建的岩芯顶部SST为27.9 ℃，末次冰盛期（Last Glacial Maximum，简称LGM，约23~19 ka）SST最低值为26.1 ℃，比晚全新世（2~0 ka）低近2 ℃。结合热带西太平洋的其他记录并对比东太平洋冷舌（Eastern Pacific Cold Tongue，简称EPCT）区的古温度重建结果，发现过去450 ka的冰期热带东-西太平洋温度梯度均大于3 ℃，WPWP温跃层变深，且间冰期的主要冰阶（MIS 5b、MIS 7d、MIS 9b）热带太平洋也呈现了较大的纬向温度梯度，最大可达到4~5 ℃。热带太平洋纬向温度梯度的变化指示，过去几十万年来气候偏冷的冰期和间冰期的冰阶热带太平洋呈现出类La Ni?a的状态，而气候变暖期间则更趋向于类El Ni?o的状态。气候变暖过程中，地表温度升高，对流层下层水汽含量快速增加导致的边界层与对流层质量交换减弱，可能使得纬向环流减弱、东-西太平洋温度梯度减小，热带太平洋表现出更类似El Ni?o的状态。
关键词: 西太平洋暖池(WPWP)/
表层海水温度(SST)/
温度梯度/
类ENSO状态

Abstract:As the strongest inter-annual climate anomaly in modern times, the El Ni?o-Southern Oscillation(ENSO)process has a significant impact on the global climate and marine hydrological conditions. On the long-term scale, the ENSO-like transition of thermal state in the tropical Pacific may also have played an important role in the paleoclimatic evolution. Most of the existing studies on the tropical ENSO-like state are, however, limited to the last glacial period, and there are many significant disagreements among these available results derived from different proxies.
Site U1486, 211.2 m in length, was drilled within the Manus Basin, the central sector of the Western Pacific Warm Pool(WPWP), at 02°22.34'S, 144°36.08'E in 1332 m of water during the International Ocean Discovery Program(IODP)Expedition 363. The site is located ca. 150 km away from the Sepik River mouth in Papua New Guinea. The tectonic setting of this area was shaped by the oblique northward movement of the Australian plate as it rapidly converged with the Pacific plate. Site U1486 is situated in the North Bismarck microplate which is resulted from the tectonic movements.
In this study, the upper 31 m core composite depth below seafloor(CCSF)of Site U1486, with lithology dominated by white foraminifera-rich nannofossil ooze, was used to reconstruct the sea surface temperature(SST)based on δ¹⁸O and Mg/Ca analyses of planktonic foraminifera Trilobatus sacculife, and thus to investigate the potential linkage between the warm/cold periods in the glacial/interglacial cycles and the tropical ENSO-like state in the WPWP since 450 ka. In more details, the age model was determined by 12 age tie points, derived from correlating the present δ¹⁸O curve with the standard LR04 stack as well as the last occurrence of Globigerinoides ruber(pink)with a well-known age(120 ka)in the west Pacific. In addition, the δ¹⁸O analysis was made on 335 subsamples, with sampling intervals of 10 cm and thus an average temporal resolution of 1.2 ka. Furthermore, a total of 455 subsamples were analyzed for the Mg/Ca ratio, with sampling intervals of 5-cm for the top 11 m and 10-cm for the rest section of the site.
The results indicate that the SST in the WPWP since 450 ka ranged between 25.3 ℃ and 30.8 ℃, with minimum and maximum value occurred at ca. 27.8 ka and 418.7 ka, respectively. The minimum SST at the site during the Last Glacial Maximum(LGM, 23~19 ka)is nearly 2 ℃ lower than that during the Late Holocene(2~0 ka). By comparing the SST records derived from the cores located in the Western Pacific Warm Pool(WPWP)and the Eastern Pacific Cold Tongue(EPCT), it is found that the zonal temperature gradient of the tropical Pacific Ocean was more than 3 ℃, along with deeper thermocline in the WPWP, during the glacial periods. This is coincident with the SST records in other cores collected from the Eastern and Western Pacific Ocean. In addition, larger zonal temperature gradients were recorded in the major stadials of interglacial periods(MIS 5b and MIS 7d). In contrast, the temperature gradients between the West and East Pacific Ocean decreased significantly during the deglacial periods(MIS 6/ 5, MIS 8/ 7 and MIS 10/ 9).
The patterns of the zonal temperature gradient across the tropical Pacific Ocean imply that the ocean conditions therein showed more La Ni?a-like states in the colder periods and more El Ni?o-like states during the warmer stages over the past few hundred thousand years. Nevertheless, the significant fluctuations in the zonal temperature gradient also indicate the instability of ENSO-like states in the tropical Pacific Ocean over a longer time-scale. When the earth-surface temperature rises, the rapid increase of water vapor concentration in the lower troposphere could weaken the mass exchange between the boundary layer and the troposphere, and thus slow down the zonal atmosphere circulation in the tropical Pacific Ocean that may result in a decreased zonal temperature gradient with a more El Ni?o-like state.
Key words:Western Pacific Warm Pool(WPWP)/
sea surface temperature(SST)/
temperature gradient/
ENSO-like state



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