Pronounced changes in the deep Atlantic circulation occurred during glacial stages, which affected the global carbon distribution and the biogeochemical cycles of other elements. Previous studies demonstrated that oceanic mercury is sensitive to the same kind of processes that affect the carbon cycle in glacial–interglacial time scales. We used Hg isotopes to elucidate Hg cycling during the last two glacial–interglacial transitions in the subtropical western South Atlantic. Mass-dependent fractionation (MDF, δ202Hg) and mass-independent fractionation (MIF, Δ199Hg) show significant variations and shift toward higher and lower values during the penultimate and Last Glacial Maximum periods, respectively. δ202Hg variability is in-phase with periods of lower atmospheric CO2 and benthic δ13C, suggesting that MDF is affected by the same mechanisms that led to atmospheric CO2 drawdown during glacial stages. In contrast, terrestrial Hg input to our site, boosted by lower sea level and exposure of the continental shelf, dominates the Δ199Hg variability.

中文翻译：

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南大西洋西部冰川二氧化碳下降与汞循环之间的关系：同位素洞察

大西洋深部环流的显着变化发生在冰期，影响了全球碳分布和其他元素的生物地球化学循环。先前的研究表明，海洋汞对影响冰期 - 间冰期时间尺度内碳循环的同类过程很敏感。我们使用 Hg 同位素来阐明在亚热带南大西洋西部最后两次冰期 - 间冰期过渡期间的 Hg 循环。质量相关分馏 (MDF, δ202Hg) 和质量无关分馏 (MIF, Δ199Hg) 分别在倒数第二个和末次盛冰期显示出显着的变化并朝着更高和更低的值移动。δ202Hg 变化与大气 CO2 较低和底栖 δ13C 的时期是同相的，表明 MDF 受到在冰川阶段导致大气 CO2 下降的相同机制的影响。相比之下，由于海平面较低和大陆架暴露的推动，我们场地的陆地汞输入主导了 Δ199Hg 的变化。