巴西边缘Mg/Ca、烯酮和TEX86衍生温度的比较研究

IF 3.2 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Paleoceanography and Paleoclimatology Pub Date : 2023-08-01 DOI:10.1029/2023PA004618

A. Bahr, A. Jaeschke, A. Hou, K. Meier, C. Chiessi, A. L. Spadano Albuquerque, J. Rethemeyer, O. Friedrich

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引用次数: 0

摘要

由于海洋在全球气候系统中的核心作用，重建准确的海面温度（SST）至关重要。然而，许多环境过程可能会对可靠的SST估计产生偏差。在这里，我们研究了海洋同位素阶段（MIS）6–5所覆盖区间的热带南大西洋西部（WTSA）SST重建的保真度，利用在巴西东部约20°S收集的岩芯。该区间是根据浮游有孔虫的Mg/Ca比率选择的先前SST估计值，表明在MIS 6期间，尽管存在冰川边界条件，但WTSA中温暖地表水的特殊汇集。为了证实基于Mg/Ca的SST数据，我们使用烯酮和TEX86古温度计在同一岩芯材料上生成了SST重建。与基于烯酮的温度估计值的比较证实了之前基于Mg/Ca的SST重建，支持MIS 6期间温水异常的建议。相比之下，TEX86衍生的温度，尽管代表了最近岩心顶部样本中的年平均SST，但比基于Mg/Ca和烯酮的SST重建低6°C。我们将异常寒冷的TEX86温度时期解释为TEX86生产者（异养海洋Thaumarchaeota）在河流悬浮液输入增加阶段的食物可用性之后向更大的水深垂直迁移的结果。同样，数据表明，与TEX86相比，基于烯酮的SST受到河流径流和/或水生藻类生长季节的季节性偏差的影响，尽管程度较小。

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A Comparison Study of Mg/Ca‐, Alkenone‐, and TEX86‐Derived Temperatures for the Brazilian Margin

The reconstruction of accurate sea‐surface temperatures (SST) is of utmost importance due to the ocean's central role in the global climate system. Yet, a number of environmental processes might bias reliable SST estimations. Here, we investigate the fidelity of SST reconstructions for the western tropical South Atlantic (WTSA) for the interval covered by Marine Isotope Stages (MIS) 6–5, utilizing a core collected off eastern Brazil at ∼20°S. This interval was selected as previous SST estimates based on Mg/Ca ratios of planktic foraminifera suggested a peculiar pooling of warm surface waters in the WTSA during MIS 6 despite glacial boundary conditions. To ground‐truth the Mg/Ca‐based SST data we generated SST reconstructions on the same core material using the alkenone and TEX86 paleothermometers. Comparison with alkenone‐based temperature estimates corroborate the previous Mg/Ca‐based SST reconstructions, supporting the suggestion of a warm‐water anomaly during MIS 6. In contrast, TEX86‐derived temperatures, albeit representing annual mean SST in recent core top samples, are up to 6°C colder than Mg/Ca‐ and alkenone‐based SST reconstructions. We interpret the periods of anomalously cold TEX86‐temperatures as a result of a vertical migration of the TEX86 producers (heterotrophic marine Thaumarchaeota) toward greater water depths, following food availability during phases of enhanced fluvial suspension input. Likewise, the data suggest that alkenone‐based SST are, albeit to a minor degree when compared to TEX86, affected by river run‐off and/or a seasonal bias in the growth season of haptophyte algae.

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来源期刊

Paleoceanography and Paleoclimatology Earth and Planetary Sciences-Atmospheric Science

CiteScore

6.20

自引率

11.40%

发文量

107

期刊介绍： Paleoceanography and Paleoclimatology (PALO) publishes papers dealing with records of past environments, biota and climate. Understanding of the Earth system as it was in the past requires the employment of a wide range of approaches including marine and lacustrine sedimentology and speleothems; ice sheet formation and flow; stable isotope, trace element, and organic geochemistry; paleontology and molecular paleontology; evolutionary processes; mineralization in organisms; understanding tree-ring formation; seismic stratigraphy; physical, chemical, and biological oceanography; geochemical, climate and earth system modeling, and many others. The scope of this journal is regional to global, rather than local, and includes studies of any geologic age (Precambrian to Quaternary, including modern analogs). Within this framework, papers on the following topics are to be included: chronology, stratigraphy (where relevant to correlation of paleoceanographic events), paleoreconstructions, paleoceanographic modeling, paleocirculation (deep, intermediate, and shallow), paleoclimatology (e.g., paleowinds and cryosphere history), global sediment and geochemical cycles, anoxia, sea level changes and effects, relations between biotic evolution and paleoceanography, biotic crises, paleobiology (e.g., ecology of “microfossils” used in paleoceanography), techniques and approaches in paleoceanographic inferences, and modern paleoceanographic analogs, and quantitative and integrative analysis of coupled ocean-atmosphere-biosphere processes. Paleoceanographic and Paleoclimate studies enable us to use the past in order to gain information on possible future climatic and biotic developments: the past is the key to the future, just as much and maybe more than the present is the key to the past.