Past Carbonate Preservation Events in the Deep Southeast Atlantic Ocean (Cape Basin) and Their Implications for Atlantic Overturning Dynamics and Marine Carbon Cycling
Past Carbonate Preservation Events in the Deep Southeast Atlantic Ocean (Cape Basin) and Their Implications for Atlantic Overturning Dynamics and Marine Carbon Cycling
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DOI：
10.1029/2018pa003353
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发表时间：
2018-06
影响因子：
3.5
通讯作者：
J. Gottschalk;D. Hodell;L. Skinner;S. Crowhurst;S. Jaccard;C. Charles
中科院分区：
文献类型：
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作者：
J. Gottschalk;D. Hodell;L. Skinner;S. Crowhurst;S. Jaccard;C. Charles
微体古生物学和地球化学分析显示，在强烈和长期的格陵兰海间沉积期间，东南大西洋深处（开普盆地）碳酸盐保存的千年尺度增加，叠加在碳酸盐埋藏的长期（轨道尺度）变化上。这些数据表明，碳酸盐过饱和的深大西洋和加强大西洋经向翻转环流（AMOC）在最激烈的格陵兰interstadials。然而，从好望角盆地以外的代理证据表明，AMOC的变化也发生在较弱和较短的格陵兰interstadials。在这里，我们通过使用毫米级X射线荧光（XRF）扫描数据重建碳酸盐保存的百年变化，重新审视了过去40万年（沉积物岩心TN 057 - 21，TN 057 - 10和大洋钻探计划1089号站点）深开普盆地AMOC动力学和碳酸盐饱和度之间的联系。我们观察到的XRF钙/钛，沉积碳酸盐含量，有孔虫壳碎片的变化之间的密切联系，反映了一个共同的控制，主要是通过改变深水碳酸盐饱和度。我们认为，XRF Ca/Ti记录的高频（亚轨道）分量表明，在长/强和短/弱的北大西洋气候异常期间，大西洋盆地中碳酸盐离子通过AMOC快速和经常性的再分布。相比之下，低频（轨道）XRF Ca/Ti分量被解释为反映了通过碳酸盐补偿和/或深海呼吸碳含量变化的缓慢调整。我们的研究结果强调了在过去的冰川期海洋碳酸盐系统的快速AMOC变化的经常性影响，提供了一个机制，通过南大洋转移北大西洋气候异常的影响，全球碳循环。
Micropaleontological and geochemical analyses reveal distinct millennial‐scale increases in carbonate preservation in the deep Southeast Atlantic (Cape Basin) during strong and prolonged Greenland interstadials that are superimposed on long‐term (orbital‐scale) changes in carbonate burial. These data suggest carbonate oversaturation of the deep Atlantic and a strengthened Atlantic Meridional Overturning Circulation (AMOC) during the most intense Greenland interstadials. However, proxy evidence from outside the Cape Basin indicates that AMOC changes also occurred during weaker and shorter Greenland interstadials. Here we revisit the link between AMOC dynamics and carbonate saturation in the deep Cape Basin over the last 400 kyr (sediment cores TN057‐21, TN057‐10, and Ocean Drilling Program Site 1089) by reconstructing centennial changes in carbonate preservation using millimeter‐scale X‐ray fluorescence (XRF) scanning data. We observe close agreement between variations in XRF Ca/Ti, sedimentary carbonate content, and foraminiferal shell fragmentation, reflecting a common control primarily through changing deep water carbonate saturation. We suggest that the high‐frequency (suborbital) component of the XRF Ca/Ti records indicates the fast and recurrent redistribution of carbonate ions in the Atlantic basin via the AMOC during both long/strong and short/weak North Atlantic climate anomalies. In contrast, the low‐frequency (orbital) XRF Ca/Ti component is interpreted to reflect slow adjustments through carbonate compensation and/or changes in the deep ocean respired carbon content. Our findings emphasize the recurrent influence of rapid AMOC variations on the marine carbonate system during past glacial periods, providing a mechanism for transferring the impacts of North Atlantic climate anomalies to the global carbon cycle via the Southern Ocean.