Paleoceanography and Paleoclimatology最新文献_第9页

Incoherency in Central American Hydroclimate Proxy Records Spanning the Last Millennium 中美洲过去一千年水文气候代用记录的不一致性

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-03-01 DOI: 10.1029/2022PA004445

Jonathan Obrist‐Farner, B. Steinman, N. Stansell, J. Maurer

{"title":"Incoherency in Central American Hydroclimate Proxy Records Spanning the Last Millennium","authors":"Jonathan Obrist‐Farner, B. Steinman, N. Stansell, J. Maurer","doi":"10.1029/2022PA004445","DOIUrl":"https://doi.org/10.1029/2022PA004445","url":null,"abstract":"Continued global warming is expected to result in reduced precipitation and a drier climate in Central America. Projections of future changes are highly uncertain, however, due to the spatial resolution limitations of models and insufficient observational data coverage across space and time. Paleoclimate proxy data are therefore critical for understanding regional climate responses during times of global climate reorganization. Here we present two lake‐sediment based records of precipitation variability in Guatemala along with a synthesis of Central American hydroclimate records spanning the last millennium (800–2000 CE). The synthesis reveals that regional climate changes have been strikingly heterogeneous, even over relatively short distances. Our analysis further suggests that shifts in the mean position of the Intertropical Convergence Zone, which have been invoked by numerous studies to explain variability in Central American and circum‐Caribbean proxy records, cannot alone explain the observed pattern of hydroclimate variability. Instead, interactions between several ocean‐atmosphere processes and their disparate influences across variable topography appear to have resulted in complex precipitation responses. These complexities highlight the difficulty of reconstructing past precipitation changes across Central America and point to the need for additional paleo‐record development and analysis before the relationships between external forcing and hydroclimate change can be robustly determined. Such efforts should help anchor model‐based predictions of future responses to continued global warming.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48665780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Exploring Icehouse Cyclicity Pattern and Seawater Dynamics on an Ancient Carbonate Platform With Nd Isotopes (Carboniferous, Southern Kazakhstan) 用Nd同位素研究哈萨克斯坦南部石炭系古碳酸盐岩台地冰窖旋回模式及海水动力学

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-03-01 DOI: 10.1029/2022PA004587

Z. Belka, S. Skompski, M. Jakubowicz, J. Dopieralska, A. Walczak, S. Mustapayeva

{"title":"Exploring Icehouse Cyclicity Pattern and Seawater Dynamics on an Ancient Carbonate Platform With Nd Isotopes (Carboniferous, Southern Kazakhstan)","authors":"Z. Belka, S. Skompski, M. Jakubowicz, J. Dopieralska, A. Walczak, S. Mustapayeva","doi":"10.1029/2022PA004587","DOIUrl":"https://doi.org/10.1029/2022PA004587","url":null,"abstract":"Over the past decades, neodymium (Nd) isotopes have received considerable attention in paleoceanography as a tool for reconstructing past seawater circulation, local weathering inputs, and sea‐level change. In this study, we have investigated the Nd isotope composition of a shallow‐water Serpukhovian (Carboniferous) carbonate succession to explore icehouse cyclicity pattern and seawater dynamics on the Karatau carbonate platform in southern Kazakhstan. The cyclic succession formed in response to glacio‐eustasy and composed of subtidal and intertidal limestones displays a large variation in εNd(326 Ma) values from −1.6 to +4.3, corresponding to differences in the isotopic composition of two seawater masses present in the Uralian–Turkestan Ocean during the Serpukhovian: (a) highly radiogenic deep waters and (b) less radiogenic surface waters. The Nd isotope excursions within the icehouse cycles are more complex than simple transgressive‐regressive cycles. They probably reflect a temporal pattern of the sub‐Milankovitch climatic perturbations during Carboniferous interglacial intervals. The episodic appearance of rich brachiopod communities was forced by the inflow of highly radiogenic, nutrient‐enriched waters, presumably driven by upwelling. Nd isotope analyses of cyclic intertidal and subtidal carbonates have great potential to produce high‐resolution records of seawater dynamics on shallow‐water carbonate platforms.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45109420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Interactions Between Depositional Regime and Climate Proxies in the Northern South China Sea Since the Last Glacial Maximum 末次盛冰期以来南海北部沉积制度与气候指标的相互作用

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-03-01 DOI: 10.1029/2022PA004591

Xuesong Wang, Yi Zhong, P. Clift, Yingci Feng, David J. Wilson, Stefanie Kaboth‐Bahr, A. Bahr, X. Gong, Debo Zhao, Zhong-rong Chen, Yanan Zhang, Yuhang Tian, Yuxing Liu, Xiaoyu Liu, Jiabo Liu, Wenyue Xia, Huihui Yang, Wei Cao, Qingsong Liu

{"title":"Interactions Between Depositional Regime and Climate Proxies in the Northern South China Sea Since the Last Glacial Maximum","authors":"Xuesong Wang, Yi Zhong, P. Clift, Yingci Feng, David J. Wilson, Stefanie Kaboth‐Bahr, A. Bahr, X. Gong, Debo Zhao, Zhong-rong Chen, Yanan Zhang, Yuhang Tian, Yuxing Liu, Xiaoyu Liu, Jiabo Liu, Wenyue Xia, Huihui Yang, Wei Cao, Qingsong Liu","doi":"10.1029/2022PA004591","DOIUrl":"https://doi.org/10.1029/2022PA004591","url":null,"abstract":"Sedimentary deposits from the northern South China Sea (SCS) can provide important constraints on past changes in ocean currents and the East Asian summer monsoon (EASM) in this region. However, the interpretation of such records spanning the last deglaciation is complicated because sea‐level change may also have influenced the depositional processes and patterns. Here, we present new records of grain size, clay mineralogy, and magnetic mineralogy spanning the past 24 kyr from both shallow and deep‐water sediment cores in the northern SCS. Our multi‐proxy comparison among multiple cores helps constrain the influence of sea‐level change, providing confidence in interpreting the regional climate‐forced signals. After accounting for the influence of sea‐level change, we find that these multi‐proxy records reflect a combination of changes in (a) the strength of the North Pacific Intermediate Water inflow, (b) the EASM strength, and (c) the Kuroshio Current extent. Overall, this study provides new insights into the roles of varying terrestrial weathering and oceanographic processes in controlling the depositional record on the northern SCS margin in response to climate and sea‐level fluctuations.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41963030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Correction of the IRD Influence for Paleo‐Current Flow Speed Reconstructions in Hemipelagic Sediments IRD对半深海沉积物古水流速度重建影响的校正

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-02-18 DOI: 10.1029/2022PA004500

N. Stevenard, A. Govin, C. Kissel, A. Van Toer

{"title":"Correction of the IRD Influence for Paleo‐Current Flow Speed Reconstructions in Hemipelagic Sediments","authors":"N. Stevenard, A. Govin, C. Kissel, A. Van Toer","doi":"10.1029/2022PA004500","DOIUrl":"https://doi.org/10.1029/2022PA004500","url":null,"abstract":"Reconstructions of past changes in deep‐sea current intensities are needed to understand ocean‐climate interactions in the past. The mean size of the sortable silt fraction (10–63 μm, SS‾ $overline{SS}$ ) is one of the most used proxies in this domain. However, in polar and subpolar environments under relatively low flow speed conditions, the presence of Ice‐Rafted Detritus (IRD) may alter the SS‾ $overline{SS}$ record and thus bias the interpretation of paleo‐current strength changes. In this paper, we examine the influence of IRD on the SS‾ $overline{SS}$ record of three sedimentary cores from the subpolar North Atlantic and the Antarctic margin. The influence of unsorted IRD on SS‾ $overline{SS}$ records is clearly established. To remove this IRD influence on grain‐size distributions (GSDs), we propose a new method based on End‐Member Analysis approach, and for which a MATLAB script is made available. This method characterizes the GSD of the unsorted IRD input, allowing it to be isolated and discarded, and the current sensitive SS‾ $overline{SS}$ variability to be robustly identified. The method therefore allows the recalculation of a modified sediment GSD free of unsorted IRD influence and the construction of modified SS‾ $overline{SS}$ and sortable silt percentage (the % of the 10–63 μm in the total <63 μm fraction) records. The application of the method to the three studied cores shows that (a) the unsorted IRD component is correctly removed from the grain‐size signal and (b) the new SS‾ $overline{SS}$ record is consistent with the XRF‐based ln(Zr/Rb) grain‐size proxy.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45999800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

The Relationship Between the Global Mean Deep‐Sea and Surface Temperature During the Early Eocene 早始新世全球平均深海与地表温度的关系

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-02-17 DOI: 10.1029/2022PA004532

Barbara Goudsmit‐Harzevoort, A. Lansu, M. Baatsen, A. S. von der Heydt, N. D. de Winter, Yurui Zhang, A. Abe‐Ouchi, A. D. de Boer, W. Chan, Y. Donnadieu, D. Hutchinson, G. Knorr, J. Ladant, P. Morozova, I. Niezgodzki, S. Steinig, A. Tripati, Zhongshi Zhang, Jiang Zhu, M. Ziegler

{"title":"The Relationship Between the Global Mean Deep‐Sea and Surface Temperature During the Early Eocene","authors":"Barbara Goudsmit‐Harzevoort, A. Lansu, M. Baatsen, A. S. von der Heydt, N. D. de Winter, Yurui Zhang, A. Abe‐Ouchi, A. D. de Boer, W. Chan, Y. Donnadieu, D. Hutchinson, G. Knorr, J. Ladant, P. Morozova, I. Niezgodzki, S. Steinig, A. Tripati, Zhongshi Zhang, Jiang Zhu, M. Ziegler","doi":"10.1029/2022PA004532","DOIUrl":"https://doi.org/10.1029/2022PA004532","url":null,"abstract":"Estimates of global mean near‐surface air temperature (global SAT) for the Cenozoic era rely largely on paleo‐proxy data of deep‐sea temperature (DST), with the assumption that changes in global SAT covary with changes in the global mean deep‐sea temperature (global DST) and global mean sea‐surface temperature (global SST). We tested the validity of this assumption by analyzing the relationship between global SST, SAT, and DST using 25 different model simulations from the Deep‐Time Model Intercomparison Project simulating the early Eocene Climatic Optimum (EECO) with varying CO2 levels. Similar to the modern situation, we find limited spatial variability in DST, indicating that local DST estimates can be regarded as a first order representative of global DST. In line with previously assumed relationships, linear regression analysis indicates that both global DST and SAT respond stronger to changes in atmospheric CO2 than global SST by a similar factor. Consequently, this model‐based analysis validates the assumption that changes in global DST can be used to estimate changes in global SAT during the early Cenozoic. Paleo‐proxy estimates of global DST, SST, and SAT during EECO show the best fit with model simulations with a 1,680 ppm atmospheric CO2 level. This matches paleo‐proxies of EECO atmospheric CO2, indicating a good fit between models and proxy‐data.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43873509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Revisiting the Geographical Extent of Exceptional Warmth in the Early Paleogene Southern Ocean 南大洋早古近纪异常温暖的地理范围再认识

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-02-16 DOI: 10.1029/2022PA004529

J. Frieling, S. Bohaty, M. Cramwinckel, S. Gallagher, G. Holdgate, T. Reichgelt, F. Peterse, J. Pross, A. Sluijs, P. Bijl

{"title":"Revisiting the Geographical Extent of Exceptional Warmth in the Early Paleogene Southern Ocean","authors":"J. Frieling, S. Bohaty, M. Cramwinckel, S. Gallagher, G. Holdgate, T. Reichgelt, F. Peterse, J. Pross, A. Sluijs, P. Bijl","doi":"10.1029/2022PA004529","DOIUrl":"https://doi.org/10.1029/2022PA004529","url":null,"abstract":"To assess zonal temperature and biogeographical patterns in the Southern Ocean during the Paleogene, we present new multi‐proxy air‐ and sea‐surface temperature data for the latest Paleocene (∼57–56 Ma) and the Paleocene‐Eocene Thermal Maximum (PETM; ∼56 Ma) from the northern margin of the Australo‐Antarctic Gulf (AAG). The various proxy data sets document the well‐known late Paleocene warming and, superimposed, two transient late Paleocene pre‐cursor warming events, hundreds of kyr prior to the PETM. Remarkably, temperature reconstructions for the AAG and southwest Pacific during the latest Paleocene, PETM and Early Eocene Climatic Optimum (∼53–49 Ma) show similar trends as well as similar absolute temperatures east and west of the closed Tasmanian Gateway. Our data imply that the exceptional warmth as recorded by previous studies for the southwest Pacific extended westward into the AAG. This contrasts with modeling‐derived circulation and temperature patterns. We suggest that simulations of ocean circulation underestimate heat transport in the southwest Pacific due to insufficient resolution, not allowing for mesoscale eddy‐related heat transport. We argue for a systematic approach to tackle model and proxy biases that may occur in marginal marine settings and non‐analog high‐latitude climates to assess the temperature reconstructions.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48778392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Weakening of the Summer Monsoon Over the Past 150 Years Shown by a Tree‐Ring Record From Shandong, Eastern China, and the Potential Role of North Atlantic Climate 从中国东部山东的树木年轮记录看近150年来夏季风的减弱以及北大西洋气候的潜在作用

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-02-15 DOI: 10.1029/2022PA004495

Qiaomei Chen, Xiaojian Zhang, F. Chen, Heli Zhang, Yu-jiang Yuan, Shulong Yu, M. Hadad, F. Roig

{"title":"Weakening of the Summer Monsoon Over the Past 150 Years Shown by a Tree‐Ring Record From Shandong, Eastern China, and the Potential Role of North Atlantic Climate","authors":"Qiaomei Chen, Xiaojian Zhang, F. Chen, Heli Zhang, Yu-jiang Yuan, Shulong Yu, M. Hadad, F. Roig","doi":"10.1029/2022PA004495","DOIUrl":"https://doi.org/10.1029/2022PA004495","url":null,"abstract":"The causes of the decreased intensity of the East Asian summer monsoon (EASM) over the past 150 years are still not fully understood, although several studies have linked the monsoon weakening to the warming of tropical oceans. Here, we use pine tree‐rings to reconstruct the precipitation total for April–August from 1810 to 2018, in south‐central Shandong Province, in the EASM region. The reconstruction accounts for 41.8% of the instrumental precipitation variance during 1965–2018. The EASM precipitation reconstruction shows extreme pluvial conditions in 1832, 1833, 1886, and 1998, and extreme droughts in 1878, 1901, and 1910, which correspond precisely to extreme climatic events recorded in historical documents. The reconstructed precipitation reveals a drying trend since the 1870s, which matches well with the decreasing trend of the EASM inferred from stalagmite oxygen isotope (δ18O) records and climate simulations. The trend of decreasing precipitation since the 1870s, indicated by our reconstruction, is significantly correlated with the spring sea surface temperature (SST) of the North Atlantic Ocean, which suggests that the EASM weakening was linked to North Atlantic SST variations during the past 150 years. This potential role of North Atlantic SST variability is supported by climate sensitivity simulations of the Community Earth System Model. North Atlantic SST variability induces two teleconnections of Rossby‐like wave propagation from the North Atlantic into East Asia, resulting in anomalous precipitation in this region.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47679060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A brGDGT‐Based Reconstruction of Terrestrial Temperature From the Maritime Continent Spanning the Last Glacial Maximum 基于brdgt的末次盛冰期海洋大陆陆地温度重建

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-02-13 DOI: 10.1029/2022PA004501

M. Parish, X. Du, S. Bijaksana, J. Russell

{"title":"A brGDGT‐Based Reconstruction of Terrestrial Temperature From the Maritime Continent Spanning the Last Glacial Maximum","authors":"M. Parish, X. Du, S. Bijaksana, J. Russell","doi":"10.1029/2022PA004501","DOIUrl":"https://doi.org/10.1029/2022PA004501","url":null,"abstract":"The tropics exert enormous influence on global climate. Despite the importance of tropical regions, the terrestrial temperature history in the Indo‐Pacific Warm Pool (IPWP) region during the last deglaciation is poorly constrained. Although numerous sea surface temperature (SST) reconstructions provide estimates of SST warming from the Last Glacial Maximum to the Holocene, the timing of the onset of deglacial warming varies between records and inhibits determining the forcings driving deglacial warming in the IPWP. We present a 60,000‐year long temperature reconstruction based on branched glycerol dialkyl glycerol tetraethers (brGDGTs) in a sediment core from Lake Towuti, located in Sulawesi, Indonesia. BrGDGTs are bacterial membrane‐spanning lipids that, globally, become more methylated with decreasing temperature and more cyclized with decreasing pH. Although changes in temperature are the dominant control on brGDGTs in regional and global calibrations, we find that the cyclization of the brGDGTs is a major mode of variation at Lake Towuti that records important changes in the lacustrine biogeochemical environment. We separate the influence of lake chemistry changes from temperature changes on the brGDGT records, and develop a temperature record spanning the last 60,000 years. The timing of the deglacial warming in our record occurs after the onset of the deglacial increase in CO2 concentrations, which suggests rising greenhouse gas concentrations and the associated radiative forcing may have forced deglacial warming in the IPWP. Peaks in temperature around 55 and 34 ka indicate that Northern Hemisphere summer insolation may also influence land surface temperature in the IPWP region.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41648404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Climate Variations in the Past 250 Million Years and Contributing Factors 过去2.5亿年的气候变化及其影响因素

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-02-01 DOI: 10.1029/2022PA004503

Xiang Li, Yongyun Hu, Jun Yang, Mengyu Wei, Jiaqi Guo, Jiawenjing Lan, Qifan Lin, Shuai Yuan, Jian Zhang, Qiang Wei, Yonggang Liu, Jianqiang Nie, Y. Xia, Shineng Hu

{"title":"Climate Variations in the Past 250 Million Years and Contributing Factors","authors":"Xiang Li, Yongyun Hu, Jun Yang, Mengyu Wei, Jiaqi Guo, Jiawenjing Lan, Qifan Lin, Shuai Yuan, Jian Zhang, Qiang Wei, Yonggang Liu, Jianqiang Nie, Y. Xia, Shineng Hu","doi":"10.1029/2022PA004503","DOIUrl":"https://doi.org/10.1029/2022PA004503","url":null,"abstract":"We simulate climate variations in the past 250 million years (Myr), using the fully coupled Community Earth System Model version 1.2.2 (CESM1.2.2) with the Community Atmosphere Model version 4 (CAM4). Three groups of simulations are performed, each including 26 simulations, with a 10‐million‐year interval. The Control group is constrained by paleogeography, increasing solar radiation, and reconstructed global mean surface temperatures (GMSTs) by tuning CO2 concentrations. No ice sheets are prescribed for all simulations except for the pre‐industrial (PI) simulation in which modern geography, ice sheets and vegetation are used. Simulated zonal mean surface temperatures are always higher than those of proxy reconstructions in the tropics, but lower than those of proxy reconstructions at middle latitudes. The relative importance of individual contributing factors for surface temperature variations in the past 250 Myr is diagnosed, using the energy‐balance analysis. Results show that greenhouse gases are the major driver in regulating GMST variations, with a maximum contribution of 12.2°C. Varying surface albedo contributes to GMST variations by 3.3°C. Increasing solar radiation leads to GMST increases by 1.5°C. Cloud radiative effects have relatively weak impacts on GMST variations, less than ±0.8°C. For comparison, two groups of sensitivity simulations are performed. One group has the CO2 concentration fixed at 10 times the PI value, and the other group has fixed CO2 concentration of 10 times the PI value and fixed solar radiation at the present‐day value, showing that varying both paleogeography and solar constant and varying paleogeography alone result in GMST changes by 7.3°C and 5.6°C, respectively.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45341089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene 基于硼同位素的大气CO2浓度与上新世全球碳循环模拟

IF 3.5 2区地球科学

Paleoceanography and Paleoclimatology Pub Date : 2023-02-01 DOI: 10.1029/2022PA004439

P. Köhler

{"title":"Atmospheric CO2 Concentration Based on Boron Isotopes Versus Simulations of the Global Carbon Cycle During the Plio‐Pleistocene","authors":"P. Köhler","doi":"10.1029/2022PA004439","DOIUrl":"https://doi.org/10.1029/2022PA004439","url":null,"abstract":"Atmospheric carbon dioxide concentrations (pCO2) beyond ice core records have been reconstructed from δ11B derived from planktic foraminifera found in equatorial sediment cores. Here, I applied a carbon cycle model over the Plio‐Pleistocene to evaluate the assumptions leading to these numbers. During glacials times, simulated atmospheric pCO2 was unequilibrated with pCO2 in the equatorial surface ocean by up to 35 ppm while the δ11B‐based approaches assume unchanged (quasi)equilibrium between both. In the Pliocene, δ11B‐based estimates of surface ocean pH are lower in the Pacific than in the Atlantic resulting in higher calculated pCO2. This offset in pH between ocean basins is not supported by models. To calculate pCO2 in surface waters out of the δ11B‐based pH some assumptions on either total alkalinity or dissolved inorganic carbon are necessary. However, the assumed values of these under‐constrained variables were according to my results partly inconsistent with chemically possible combinations within the marine carbonate system. The model results show glacial/interglacial variability in total alkalinity of the order of 100 μmol/kg, which is rarely applied to proxy reconstructions. Simulated atmospheric pCO2 is tightly (r2 > 0.9) related to equatorial surface‐ocean pH, which can be used for consistency checks. Long‐term trends in volcanic CO2 outgassing and the strength of the continental weathering fluxes are still unconstrained, allowing for a wide range of possible atmospheric pCO2 across the Plio‐Pleistocene. Nevertheless, this carbon cycle analysis suggests that reported atmospheric pCO2 above 500 ppm in the Pliocene might, for various reasons, need to be revised to smaller numbers.","PeriodicalId":54239,"journal":{"name":"Paleoceanography and Paleoclimatology","volume":" ","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42654806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0