The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink.
The seasonal sea-ice zone in the glacial Southern Ocean as a carbon sink.
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DOI：
10.1038/ncomms9136
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发表时间：
2015-09-18
影响因子：
16.6
通讯作者：
Tiedemann R
中科院分区：
文献类型：
--
作者：
Abelmann A;Gersonde R;Knorr G;Zhang X;Chapligin B;Maier E;Esper O;Friedrichsen H;Lohmann G;Meyer H;Tiedemann R
南大洋表层-深海交换的减少和浮游植物营养消耗的增加与冰川大气二氧化碳含量的降低有关。然而，所涉及的生物和物理条件以及相关过程的确定仍然不完整。在这里，我们使用一种新的工具，硅藻和放射虫蛋白石的氧和硅联合同位素测量，结合数值模拟，指定南大洋表面-地下对比。我们的数据并不表明存在与冰山融水有关的永久冰川盐斜。通过数值模拟，我们发现冰川表面分层是可变的，并且与季节性海冰变化有关。在冰川春夏期间，混合层相对较浅，而在秋冬期间发生较深的混合，允许表层海洋补充深层水库的营养物质，这些营养物质可能比现在更丰富。这产生了特定的碳和蛋白石输出机制，将冰川季节性海冰带变成了碳汇。冰川大气中较低的二氧化碳含量与南大洋碳储量的增加有关，但相关的生物和物理机制尚不清楚。在这里，作者结合硅藻和放射虫的同位素测量和模型模拟来研究地表-地下过程。
Reduced surface–deep ocean exchange and enhanced nutrient consumption by phytoplankton in the Southern Ocean have been linked to lower glacial atmospheric CO2. However, identification of the biological and physical conditions involved and the related processes remains incomplete. Here we specify Southern Ocean surface–subsurface contrasts using a new tool, the combined oxygen and silicon isotope measurement of diatom and radiolarian opal, in combination with numerical simulations. Our data do not indicate a permanent glacial halocline related to melt water from icebergs. Corroborated by numerical simulations, we find that glacial surface stratification was variable and linked to seasonal sea-ice changes. During glacial spring–summer, the mixed layer was relatively shallow, while deeper mixing occurred during fall–winter, allowing for surface-ocean refueling with nutrients from the deep reservoir, which was potentially richer in nutrients than today. This generated specific carbon and opal export regimes turning the glacial seasonal sea-ice zone into a carbon sink. Lower glacial atmospheric CO2 has been linked to enhanced carbon storage in the Southern Ocean, yet the associated biological and physical mechanisms are poorly understood. Here, the authors combine diatom and radiolarian isotope measurements, and model simulations to investigate surface–subsurface processes.