Intensive mixing along an island chain controls oceanic biogeochemical cycles
Intensive mixing along an island chain controls oceanic biogeochemical cycles
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DOI：
10.1002/gbc.20088
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发表时间：
2013-09
影响因子：
5.2
通讯作者：
J. Nishioka;T. Nakatsuka;Y. Watanabe;I. Yasuda;K. Kuma;H. Ogawa;N. Ebuchi;Alexey I. Scherbinin
中科院分区：
文献类型：
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作者：
J. Nishioka;T. Nakatsuka;Y. Watanabe;I. Yasuda;K. Kuma;H. Ogawa;N. Ebuchi;Alexey I. Scherbinin
亚北极太平洋是一个高营养低叶绿素（HNLC）区域，其中浮游植物的生长受到铁（Fe）可用性的广泛限制。然而，即使与铁的限制，西部亚北极太平洋（WSP）有显着的浮游植物的增长和更大的季节性变化，在较低的营养水平比东部亚北极太平洋。因此，铁供应的差异必须解释季节性浮游植物生长从西到东的减少。在WSP的真光层的Fe通量发生在一个“中等”的值，因为它是显着高于其值的东侧，但它不足以导致广泛的常量营养素耗尽，即HNLC状态保持。虽然我们认识到几个Fe供应过程中的WSP，占这个中等值的Fe供应的机制，以前没有得到解释。在这里，我们展示了千岛群岛链（KIC）中潮汐混合对于确定中等值的关键作用。盆地尺度的纬向铁剖面显示，来自鄂霍次克海沉积物的铁通过KIC排入北太平洋西部的中间水团（~ 800 m）。这种富含Fe的中间水在穿过KIC时通过强烈混合而进行的再分配是决定微量营养素（Fe）与常量营养素（例如，硝酸盐）。这一比值可以定量地解释亚北极东西部表层常量营养元素消耗的差异，以及亚北极北太平洋HNLC沃茨的一般形成和地球化学特征。
The subarctic Pacific is a high‐nutrient low‐chlorophyll (HNLC) region in which phytoplankton growth is broadly limited by iron (Fe) availability. However, even with Fe limitation, the western subarctic Pacific (WSP) has significant phytoplankton growth and greater seasonal variability in lower trophic levels than the eastern subarctic Pacific. Therefore, differences in Fe supply must explain the west‐to‐east decrease in seasonal phytoplankton growth. The Fe flux to the euphotic zone in the WSP occurs at a “moderate” value, in that it is significantly higher than its value on the eastern side, yet it is not sufficient enough to cause widespread macronutrient depletion, that is, HNLC status is maintained. Although we recognize several Fe supply processes in the WSP, the mechanisms that account for this moderate value of Fe supply have not previously been explained. Here we demonstrate the pivotal role of tidal mixing in the Kuril Islands chain (KIC) for determining the moderate value. A basin‐scale meridional Fe section shows that Fe derived from sediments in the Sea of Okhotsk is discharged through the KIC into the intermediate water masses (~ 800 m) of the western North Pacific. The redistribution of this Fe‐rich intermediate water by intensive mixing as it crosses the KIC is the predominant process determining the ratio of micronutrient (Fe) to macronutrients (e.g., nitrate) in subsurface waters. This ratio can quantitatively explain the differences in surface macronutrient consumption between the western and eastern subarctic, as well as the general formation and biogeochemistry of HNLC waters of the subarctic North Pacific.