The oceanic chromium (Cr) cycle is mainly governed by the interconversion and the distribution of Cr(VI) and Cr(III) species and their stable isotopic ratios (δ53Cr) in the water column. As a result, the Cr cycle generates a strong correlation between the natural logarithm of its dissolved concentration and δ53Cr regardless of the location of sampling. A few studies have reported the Cr composition of certain regions falling off the global Cr array, highlighting the local prevalence of underlying mechanisms participating in the Cr cycle in the oceans. In an effort to better constrain the global Cr array, this study presents an extensive dataset for total dissolved Cr concentration ([Cr]T) and δ53Cr in the Arctic Ocean in regions meeting the environmental conditions where Cr was observed to fall off the global Cr array (e.g. continental shelves, restricted water circulation, sea ice melting). We find that more than 70% of the Arctic seawater collected plot below the global Cr array due to a small addition of highly fractionated Cr (−2.8 ‰ to −1.1 ‰) and its transport across all the Arctic regions sampled. We identify the Chukchi Shelf as the region where highly fractionated Cr is produced, from where a Cr shuttle could work in tandem with the Arctic Fe and Mn shuttles to explain the production and widespread export of isotopically light Cr in the Arctic waters. We identify a second non-reductive release of highly fractionated Cr in the Canadian Arctic Archipelago, Baffin Bay and potentially the Labrador Sea via sediment resuspension, alongside addition of isotopically light Cr originating from crustal rocks. These findings demonstrate that the Arctic-modified outflow signature of Cr isotopes modify the Cr isotopic signature of the North Atlantic waters, and that the North Atlantic waters may deviate from the global Cr array depending on whether the isotopically light Cr added to the Arctic Ocean is Cr(III) that has not been scavenged or Cr(III) that has oxidized to Cr(VI).

中文翻译：

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北冰洋高度分馏铬同位素的大陆架到盆地穿梭


海洋铬 （Cr） 循环主要受 Cr（VI） 和 Cr（III） 物种的相互转化和分布及其在水柱中的稳定同位素比 （δ53Cr） 控制。因此，无论采样位置如何，Cr 循环都会在其溶解浓度的自然对数与 δ53Cr 之间产生很强的相关性。一些研究报告了某些区域的 Cr 组成从全球 Cr 阵列中下降，突出了参与海洋 Cr 循环的潜在机制的局部普遍性。为了更好地限制全球 Cr 阵列，本研究提供了一个广泛的数据集，用于满足观察到 Cr 从全球 Cr 阵列下降的环境条件（例如大陆架、限制水循环、海冰融化）的北冰洋总溶解 Cr 浓度 （[Cr]T） 和 δ53Cr。我们发现，由于少量添加了高度分馏的 Cr （-2.8 ‰ 至 -1.1 ‰） 及其在所有采样的北极地区中的传输，超过 70% 的北极海水收集的图位于全球 Cr 阵列下方。我们将楚科奇大陆架确定为生产高度分馏 Cr 的地区，Cr 穿梭车可以与北极 Fe 和 Mn 穿梭车协同工作，以解释北极水域同位素轻 Cr 的生产和广泛出口。我们通过沉积物再悬浮在加拿大北极群岛、巴芬湾和潜在的拉布拉多海确定了高度馏分 Cr 的第二次非还原性释放，同时增加了源自地壳岩石的同位素轻 Cr。 这些发现表明，Cr 同位素的北极修饰的流出特征改变了北大西洋水域的 Cr 同位素特征，并且北大西洋水域可能会偏离全球 Cr 阵列，具体取决于添加到北冰洋的同位素轻 Cr 是尚未清除的 Cr（III） 还是已氧化成 Cr（VI） 的 Cr（III）。