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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >The Role Of Nutricline Depth In Regulating The Ocean Carbon Cycle
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The Role Of Nutricline Depth In Regulating The Ocean Carbon Cycle

机译：纽深在调节海洋碳循环中的作用

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Carbon uptake by marine phytoplankton, and its export as organic matter to the ocean interior (i.e., the "biological pump"), lowers the partial pressure of carbon dioxide (pCO_2) in the upper ocean and facilitates the diffusive drawdown of atmospheric CO_2. Conversely, precipitation of calcium carbonate by marine planktonic calcifiers such as coccolithophorids increases pCO_2 and promotes its outgassing (i.e., the "alkalinity pump"). Over the past 100 million years, these two carbon fluxes have been modulated by the relative abundance of diatoms and coccolithophores, resulting in biological feedback on atmospheric CO_2 and Earth's climate; yet, the processes determining the relative distribution of these two phytoplankton taxa remain poorly understood. We analyzed phytoplankton community composition in the Atlantic Ocean and show that the distribution of diatoms and coccolithophorids is correlated with the nutricline depth, a proxy of nutrient supply to the upper mixed layer of the ocean. Using this analysis in conjunction with a coupled atmosphere-ocean intermediate complexity model, we predict a dramatic reduction in the nutrient supply to the euphotic layer in the coming century as a result of increased thermal stratification. Our findings indicate that, by altering phytoplankton community composition, this causal relationship may lead to a decreased efficiency of the biological pump in sequestering atmospheric CO_2, implying a positive feedback in the climate system. These results provide a mechanistic basis for understanding the connection between upper ocean dynamics, the calcium carbonate-to-organic C production ratio and atmospheric pCO_2 variations on time scales ranging from seasonal cycles to geological transitions.
机译：海洋浮游植物吸收碳，并将其作为有机物输出到海洋内部（即“生物泵”），降低了上层海洋中的二氧化碳分压（pCO_2），并促进了大气CO_2的扩散扩散。相反地​​，海洋浮游钙化剂例如球墨石藻的碳酸钙的沉淀增加了pCO_2并促进了其脱气（即“碱度泵”）。在过去的一亿年中，这两个碳通量已被硅藻和球墨镜的相对丰度调节，从而产生了有关大气CO_2和地球气候的生物反馈。然而，确定这两个浮游植物类群相对分布的过程仍知之甚少。我们对大西洋中的浮游植物群落组成进行了分析，结果表明硅藻和球墨镜藻类的分布与营养深度有关，营养深度是海洋上层混合层营养的代表。结合耦合的海洋-海洋中间复杂性模型，我们可以预测，由于增加的热分层，在未来的一个世纪中，向富营养层的养分供应将大大减少。我们的发现表明，通过改变浮游植物群落组成，这种因果关系可能导致生物泵隔离大气CO_2的效率降低，这意味着气候系统中存在积极反馈。这些结果为理解高层海洋动力学，碳酸钙与有机碳的生产比率以及大气pCO_2之间的联系提供了机械基础，这些时间尺度从季节性周期到地质过渡。

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