Contribution of seasonal sub-Antarctic surface water variability to millennial-scale changes in atmospheric CO2 over the last deglaciation and Marine Isotope Stage 3
Contribution of seasonal sub-Antarctic surface water variability to millennial-scale changes in atmospheric CO2 over the last deglaciation and Marine Isotope Stage 3
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DOI：
10.1016/j.epsl.2014.11.051
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发表时间：
2015-02-01
影响因子：
5.3
通讯作者：
Waelbroeck, Claire
中科院分区：
文献类型：
--
作者：
Gottschalk, Julia;Skinner, Luke C.;Waelbroeck, Claire
南大洋被认为在过去的大气二氧化碳（CO2，（atm））变化中发挥了关键作用。据了解，三个主要因素通过影响表层海洋pCO（2）和区域海洋-大气CO2通量来控制南大洋对CO2（atm）的影响：1）海-气气体交换的效率，这可能会因季节性或年度海冰覆盖或浅密度跃层的发展而减弱; 2）来自次表层和深海的富CO2水团的供应，这与湍流混合和表面浮力和/或风强迫有关; 3）生物固碳，这取决于养分的可利用性，因此受到灰尘沉积和/或上升流的影响。为了研究这些过程可能的贡献，千年尺度的CO2，（大气压）变化在末次冰期和冰消期，我们利用南极有孔虫普查计数和稳定的氧和碳同位素测量在南极有孔虫Globigerina bulloides和Neogloboquadrina pachyderma（左）从海洋沉积物芯MD 07 - 3076 Q在亚南极大西洋。这些数据的解释的基础上，比较的核心顶部和现代海水同位素数据，这允许的季节性偏差和地球化学控制的G的稳定同位素组成的评估。bulloides和N.厚皮病根据我们的下芯结果与类似的数据从东南大西洋（海角盆地）的比较，我们推断过去的流域范围内的变化，在亚南极大西洋的表面水文。我们发现，在过去的70万年的二氧化碳（大气压）的千年尺度的上升始终与春季上升流增加的证据，并加强夏季在亚南极大西洋的海气交换。夏季出口产品增加的平行证据表明，上升流和海气交换的季节性变化对亚南极大西洋的表面pCO（2）产生了主要影响。这些结果强调了南大洋动力学的作用，特别是其季节性变化，在驱动千年尺度的变化，在CO2，（大气压）。(C)2014作者由爱思唯尔公司出版
The Southern Ocean is thought to have played a key role in past atmospheric carbon dioxide (CO2,(atm)) changes. Three main factors are understood to control the Southern Ocean's influence on CO2,(atm), via their impact on surface ocean pCO(2) and therefore regional ocean-atmosphere CO2 fluxes: 1) the efficiency of air-sea gas exchange, which may be attenuated by seasonal- or annual sea-ice coverage or the development of a shallow pycnocline; 2) the supply of CO2-rich water masses from the subsurface and the deep ocean, which is associated with turbulent mixing and surface buoyancy- and/or wind forcing; and 3) biological carbon fixation, which depends on nutrient availability and is therefore influenced by dust deposition and/or upwelling. In order to investigate the possible contributions of these processes to millennial-scale CO2,(atm) variations during the last glacial and deglacial periods, we make use of planktonic foraminifer census counts and stable oxygen- and carbon isotope measurements in the planktonic foraminifera Globigerina bulloides and Neogloboquadrina pachyderma (sinistral) from marine sediment core MD07-3076Q in the sub-Antarctic Atlantic. These data are interpreted on the basis of a comparison of core-top and modern seawater isotope data, which permits an assessment of the seasonal biases and geochemical controls on the stable isotopic compositions of G. bulloides and N. pachyderma (s.). Based on a comparison of our down-core results with similar data from the Southeast Atlantic (Cape Basin) we infer past basin-wide changes in the surface hydrography of the sub-Antarctic Atlantic. We find that millennial-scale rises in CO2,(atm) over the last 70 ka are consistently linked with evidence for increased spring upwelling, and enhanced summer air-sea exchange in the sub-Antarctic Atlantic. Parallel evidence for increased summer export production would suggest that seasonal changes in upwelling and air-sea exchange exerted a dominant influence on surface pCO(2) in the sub-Antarctic Atlantic. These results underline the role of Southern Ocean dynamics, in particular their seasonal variations, in driving millennial-scale variations in CO2,(atm). (C) 2014 The Authors. Published by Elsevier B.V.