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首页> 外文期刊>Paleoceanography >Evidence from diatom-bound nitrogen isotopes for subarctic Pacific stratification during the last ice age and a link to North Pacific denitrification changes
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Evidence from diatom-bound nitrogen isotopes for subarctic Pacific stratification during the last ice age and a link to North Pacific denitrification changes

机译：在最后一个冰期，硅藻结合的氮同位素为北极亚太平洋太平洋分层提供了证据，并且与北太平洋反硝化变化有关

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[1] In a piston core from the central Bering Sea, diatom microfossil-bound N isotopes and the concentrations of opal, biogenic barium, calcium carbonate, and organic N are measured over the last glacial/interglacial cycle. Compared to the interglacial sections of the core, the sediments of the last ice age are characterized by 3 parts per thousand higher diatom-bound delta N-15, 70 wt % lower opal content and 1200 ppm lower biogenic barium. Taken together and with constraints on sediment accumulation rate, these results suggest a reduced supply of nitrate to the surface due to stronger stratification of the upper water column of the Bering Sea during glacial times, with more complete nitrate consumption resulting from continued iron supply through atmospheric deposition. This finding extends the body of evidence for a pervasive link between cold climates and polar ocean stratification. In addition, we hypothesize that more complete nutrient consumption in the glacial age subarctic Pacific contributed to the previously observed ice age reduction in suboxia and denitrification in the eastern tropical North Pacific by lowering the nutrient content of the intermediate-depth water formed in the subpolar North Pacific. In the deglacial interval of the Bering Sea record, two apparent peaks in export productivity are associated with maxima in diatom-bound and bulk sediment delta N-15. The high delta N-15 in these intervals may have resulted from greater surface nutrient consumption during this period. However, the synchroneity of the deglacial peaks in the Bering Sea with similar bulk sediment delta N-15 changes in the eastern Pacific margin and the presence of sediment lamination within the Bering Sea during the deposition of the productivity peaks raise the possibility that both regional and local denitrification worked to raise the delta N-15 of the nitrate feeding Bering Sea surface waters at these times.
机译：[1]在白令海中部的一个活塞核心中，在最后的冰川/冰川间周期中测量了硅藻与化石结合的氮同位素以及蛋白石，生物钡，碳酸钙和有机氮的浓度。与岩心的冰间断层相比，上一个冰河时期的沉积物的特征是每千分之三的硅藻结合的增量N-15，蛋白石含量降低70 wt％，生物成因钡含量降低1200 ppm。综合考虑并限制了沉积物的沉积速率，这些结果表明，由于冰河时期白令海上层水柱的分层更牢固，地表的硝酸盐供应减少，而大气中持续不断的铁供应导致硝酸盐的消耗更加完全。沉积。这一发现为寒冷气候和极地海洋分层之间普遍存在的联系提供了证据。此外，我们假设冰期亚北极太平洋中更完整的养分消耗，是通过降低北亚极地形成的中等深度水的养分含量，从而导致了先前观察到的亚氧层冰期减少和东部热带北太平洋的反硝化作用。太平洋。在白令海记录的冰期间隔中，出口生产力的两个明显峰值与硅藻结合和散装沉积物三角洲N-15的最大值相关。在此间隔内，较高的N-15增量可能是由于在此期间增加了表面养分消耗。但是，白令海的冰期峰与东太平洋边缘的相似的大体积沉积物三角洲N-15变化的同步性以及生产力峰值沉积过程中白令海内部沉积物层状的存在增加了区域性和区域性冰期峰值的同步性。在这些时候，当地的反硝化努力提高了供给白令海地表水的硝酸盐的N-15值。

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