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GUO Jingteng,LI Tiegang,XIONG Zhifang,QIU Xiaohua,CHANG Fengming. 2019. Revisiting the dependence of thermocline-dwelling foraminiferal B/Ca on temperature and [CO32-], and its application in reconstruction of the subsurface carbonate system in the tropical western Pacific since 24 ka. Acta Oceanologica Sinica, 38(9):71-86
Revisiting the dependence of thermocline-dwelling foraminiferal B/Ca on temperature and [CO32-], and its application in reconstruction of the subsurface carbonate system in the tropical western Pacific since 24 ka
再探温跃层有孔虫B/Ca与温度和[CO32-]的依赖性及其在24 ka以来热带西太平洋次表层碳酸盐系统重建中的应用
Received:April 25, 2018??
DOI:10.1007/s13131-019-1476-y
Key words:planktonic foraminifera??B/Ca??carbonate chemistry??tropical western Pacific??South China Sea
中文关键词:??浮游有孔虫??B/Ca??碳酸盐化学??热带西太平洋??中国南海
基金项目:The Open Fund of Qingdao National Laboratory for Marine Science and Technology under contract No. QNLM2016ORP0205; the Basic Scientific Fund for National Public Research Institutes of China under contract Nos 2017Y07 and 2019S04; the National Natural Science Foundation of China under contract Nos 41230959, 41830539, 91858106 and 41576051; the Taishan Scholars Project Funding; the Shandong Provincial Natural Science Foundation under contract No. ZR2016DQ17; the Scientific and Technological Innovation Project of Qingdao National Laboratory for Marine Science and Technology under contract No. 2016ASKJ13.
Author NameAffiliationE-mail
GUO Jingteng?CAS Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
University of Chinese Academy of Sciences, Beijing 100049, China?
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LI Tiegang?First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China
Laboratory for Marine Geology and Environment, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China?
zhfxiong@fio.org.cn?
XIONG Zhifang?First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China
Laboratory for Marine Geology and Environment, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China?
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QIU Xiaohua?No. 1 Institute of Geology and Mineral Resources of Shandong Province, Jinan 250014, China??
CHANG Fengming?CAS Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Laboratory for Marine Geology and Environment, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China?
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Abstract:
??????The B/Ca ratio of planktonic foraminifer shells has been used as a proxy for reconstructing past ocean carbonate chemistry. However, recent studies have revealed significant uncertainties associated with this proxy, such as whether seawater temperature or[CO32-] is the dominant control on the partition coefficient (KD) of planktonic foraminiferal B/Ca. To address these uncertainties and thus improve our understanding of the planktonic foraminiferal B/Ca proxy, we analysed B/Ca ratios in the tests of Neogloboquadrina dutertrei (300-355 μm) and Pulleniatina obliquiloculata (355-400 μm) in surface sediment samples from the tropical western Pacific and South China Sea. The relationship between these B/Ca ratios and bottom water calcite saturation states (Δ[CO32-]) is weak, thus suggesting only a small dissolution effect on the B/Ca of the two species. The correlation coefficients (R2) between the B/Ca ratios of N. dutertrei and P. obliquiloculata and environmental parameters (e.g., temperature, salinity, phosphate, DIC and ALK) in the tropical western Pacific and South China Sea are not high enough to justify using B/Ca ratios as a palaeoenvironmental proxy in the study areas. The significant correlation between KD values of N. dutertrei and P. obliquiloculata and carbonate system parameters (e.g.,[CO32-], DIC, ALK, pH and[${\rm {HCO}}_3^{-}$]) in the study area reflect chemical links between the KD denominator and these variables. Based on our surface sediment calibration, an empirical relationship between the KD of N. dutertrei and temperature is proposed in the tropical western Pacific. We also generated a record of B/Ca ratios in N. dutertrei (300-355 μm) from Core MD06-3052 in the tropical western Pacific over the past 24 ka to evaluate the application of the revised B/Ca proxy method. Based on the reconstructed empirical relationship for B/Ca and subsurface seawater ALK, we estimated subsurface seawater carbonate system parameters in the tropical western Pacific since 24 ka. In general, the estimated subsurface seawater pH and[CO32-] show an increase with time, and the record of subsurface seawater pCO2 shows a decrease with time, in the tropical western Pacific over the past 24 ka. The consistent trends in subsurface seawater pCO2 and opal flux during deglaciation may imply that the reported increase in subsurface water pCO2 in the study area was promoted by enhanced upwelling in the Southern Ocean.
中文摘要:
??????浮游有孔虫B/Ca比值已被用于过去海水碳酸盐化学的替代性指标。然而,最近的研究表明,浮游有孔虫B/Ca分配系数(KD)的主控因素是海水温度还是[CO32-]具有不确定性。为解决这些不确定性,从而提高我们对于浮游有孔虫B/Ca作为替代性指标的理解,本文测量了热带西太平洋和中国南海表层沉积物样品中有孔虫Neogloboquadrina dutertrei(300-355 μm)和Pulleniatina obliquiloculata(355-400 μm)的B/Ca比值。B/Ca比值与底层水碳酸钙饱和度(Δ[CO32-)的相关性较弱,表明溶解作用对本研究所用属种B/Ca比值的影响较小。N.dutertreiP.obliquiloculata的B/Ca比值与热带西太平洋和中国南海的环境参数(如温度、盐度、磷酸盐、溶解无机碳以及总碱度)的相关系数值(R2)不够高,难以证明B/Ca比值作为研究区内环境参数替代指标的有效性。而N.dutertreiP.obliquiloculata的KD值与研究区碳酸盐系统参数(如[CO32-]、溶解无机碳、总碱度、pH和[HCO3-])的显着相关反映了KD公式分母与这些变量之间的化学联系。基于表层沉积物校准,我们提出了热带西太平洋N.dutertrei KD值与温度的经验关系。利用24 ka以来热带西太平洋MD06-3052孔N.dutertrei(300-355 μm)的B/Ca比值记录,我们还评估了修正后B/Ca指标方法的应用性。基于重建的B/Ca指标经验关系以及次表层海水总碱度,本文估算了24 ka以来热带西太平洋次表层海水碳酸盐系统参数。总的来看,24 ka以来热带西太平洋次表层海水pH和[CO32-]随时间推移而增高,而次表层海水pCO2随时间推移而减低。此外,冰消期热带西太平洋次表层海水pCO2与蛋白石通量趋势的一致性,可能暗示了研究区次表层海水pCO2的增高是由南大洋上升流的增强所致。
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