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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Fluxes of ~(230)Th and ~(231)Pa to the deep sea: implications for the interpretation of excess ~(230)Th and ~(231)Pa/~(230)Th profiles in sediments
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Fluxes of ~(230)Th and ~(231)Pa to the deep sea: implications for the interpretation of excess ~(230)Th and ~(231)Pa/~(230)Th profiles in sediments

机译：〜（230）Th和〜（231）Pa通向深海的通量：对解释沉积物中过量〜（230）Th和〜（231）Pa /〜（230）Th剖面的影响

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Analysis of samples obtained with deep-sea moored sediment traps deployed at 15 sites representing a wide range of oceanic conditions confirms that the flux of ~(230)Th scavenged to the seafloor remains close to its production rate from the decay of ~(234)U in the overlying water column, and generally validates the use of ~(230)Th as a normalizing tool for paleoflux reconstruction. After correction for trapping efficiency, the flux of ~(230)Th measured in the low flux regions amounts to 90 ± 6% of the production rate, with the notable exceptions of one site near the Arabian Sea upwelling and one site in the Weddell Sea. A ~(230)Th flux equivalent to 120% of the production rate was found in Panama Basin. Similar or more extensive scavenging of ~(230)Th may be occurring at a Pacific margin site off California and south of the Polar Front, but these estimates are obscured by large errors on our trapping-efficiency estimates. In contrast, the flux of ~(231)Pa and the ~(231)Pa/~(230)Th ratio can vary strongly with particle flux, following distinct trends in different oceanic basins. In the Atlantic Ocean, ~(231)Pa fluxes and ~(231)Pa/~(230)Th are low and not sensitive to particle flux. This is because of the short residence time of deep water in this basin resulting from thermohaline circulation, which prevents the full development of lateral concentration gradients and full expression of boundary scavenging. In the Pacific Ocean, the sensitivity of ~(231)Pa/~(230)Th to particle flux is highest, reflecting the longer residence time of deep water. In the southern ocean, ~(231)Pa/~(230)Th ratios are invariably high, even when particle fluxes are low, reflecting the predominance of opal, which fractionates minimally between the two radionuclides. Interpretation of ~(231)Pa/~(230)Th recorded in sediments is thus complex. In the Atlantic, this ratio is better suited for recording past changes in the strength of thermohaline circulation. In the Pacific, it has the best potential for providing synoptic maps of past changes in particle flux. In the southern ocean, retrieval of information from ~(231)Pa/~(230)Th is more difficult and requires a more quantitative understanding of the influence of particle composition.
机译：对分布在15个地点的代表深海条件的深海系泊沉积物捕集阱所获得的样品进行的分析证实，〜（230）Th清除至海底的通量仍保持从〜（234）衰减以来的生产率。 U在上水柱中，通常验证〜（230）Th作为标准化通量重建的工具。校正捕集效率后，在低通量区域测得的〜（230）Th通量为生产率的90±6％，值得注意的例外是阿拉伯海上升流附近的一个地点和韦德尔海的一个地点。在巴拿马盆地发现了〜（230）Th通量，相当于产量的120％。 〜（230）Th的类似或更广泛的清除可能发生在加利福尼亚州和极地锋以南的太平洋边缘站点，但是这些估计值被我们的捕集效率估计值的较大误差所掩盖。相反，〜（231）Pa和〜（231）Pa /〜（230）Th的通量随颗粒通量的变化而变化很大，这取决于不同海洋盆地的明显趋势。在大西洋中，〜（231）Pa通量和〜（231）Pa /〜（230）Th低，并且对粒子通量不敏感。这是由于热盐环流导致该盆地深水停留时间短，这阻止了侧向浓度梯度的充分发展和边界清除的充分表达。在太平洋，〜（231）Pa /〜（230）Th对粒子通量的敏感性最高，反映了深水停留时间更长。在南部海洋中，即使粒子通量很低，〜（231）Pa /〜（230）Th比率也始终很高，这反映出蛋白石占主导地位，蛋白石在两种放射性核素之间的比例最小。因此，对沉积物中记录的〜（231）Pa /〜（230）Th的解释非常复杂。在大西洋，该比例更适合记录热盐循环强度的过去变化。在太平洋地区，它具有提供过去粒子通量变化的天气概况的最佳潜力。在南部海洋中，从〜（231）Pa /〜（230）Th中检索信息更加困难，并且需要对粒子组成的影响进行更定量的了解。

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