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Advection and scavenging controls of Pa/Th in the northern NE Atlantic

机译：北大西洋东北部对Pa / Th的对流和清除控制

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Over the last 2 decades, significant advances have been made in reconstructing past rates of ocean circulation using sedimentary proxies for the dynamics of abyssal waters. In this study we combine the use of two rate proxies, sortable silt grain size, and sedimentary ~(231)Pa/~(230)Th, measured on a depth transect of deep-sea sediment cores from the northern NE Atlantic, to investigate ocean circulation changes during the last deglacial. We find that at two deep sites, the core-top ~(231)Pa/~(230)Th ratios reflect Holocene circulation rates, while during Heinrich Stadial 1, the deglacial ratios peaked as the sortable silt grain size decreased, reflecting a general circulation slowdown. However, the peak ~(231)Pa/~(230)Th significantly exceeded the production ratio in both cores, indicating that ~(231)Pa/~(230)Th was only partially controlled by ocean circulation at these sites. This is supported by a record of ~(231)Pa/~(230)Th from an intermediate water depth site, where values also peaked during Heinrich Stadial 1, but were consistently above the production ratio over the last 24 ka, reflecting high scavenging below productive surface waters. At our study sites, we find that preserved sediment component fluxes cannot be used to distinguish between a scavenging or circulation control, although they are consistent with a circulation influence, since the core at intermediate depth with the highest ~(231)Pa/~(230)Th recorded the lowest particle fluxes. Reconstruction of advection rate using ~(231)Pa/~(230)Th in this region is complicated by high productivity, but the data nevertheless contain important information on past deep ocean circulation.
机译：在过去的20年中，在利用深海水动力的沉积代理重建过去的海洋环流速率方面取得了重大进展。在这项研究中，我们结合使用两个速率代理（可分选的粉砂颗粒大小）和沉积物〜（231）Pa /〜（230）Th（在东北大西洋北部深海沉积物芯的深度剖面上测量）来进行研究在最后一次冰期期间，海洋环流发生了变化。我们发现，在两个深部，芯顶〜（231）Pa /〜（230）Th比反映了全新世循环速率，而在海因里希球场1期间，随着可分选粉砂粒度的减小，冰消比例达到峰值，反映了总体血液循环减慢。但是，〜（231）Pa /〜（230）Th的峰值大大超过了两个岩心的产水率，表明〜（231）Pa /〜（230）Th在这些位置仅受海洋环流的控制。这由中间水深站点的〜（231）Pa /〜（230）Th记录所支持，该位置的值在Heinrich Stadial 1期间也达到峰值，但在过去24 ka期间始终高于产量，反映出较高的清除率低于生产性地表水。在我们的研究地点，我们发现保留的泥沙成分通量尽管与循环影响相一致，却不能用来区分清除还是循环控制，因为岩心处的中间深度最高〜（231）Pa /〜（ 230）Th记录了最低的粒子通量。在该地区，使用〜（231）Pa /〜（230）Th重建对流速率非常复杂，但是数据仍然包含有关过去深海环流的重要信息。

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