Modern-day ocean circulation behaves as a complex forced convective system that is characterized by the decrease in water temperature but increase in water density with depth. The dissolved oxygen content – which initially decreases due to biological oxygen demand – also increases with depth. In contrast to the present-day scenario, we propose that during the Archaean and Proterozoic eons inverted profiles could have developed such that, with depth, ocean water temperature increased and density and dissolved oxygen decreased. These inverted temperature and density profiles resulted in palaeo-ocean circulation behaving as a free convective system. It is proposed that this free convection, which may have been stable, or chaotic and subject to secondary instabilities, hindered the deep oxygenation of the palaeo-ocean. It may not be coincidental that the great oxygenation event (GOE) and Huronian glaciations are contemporaneous, in a similar way that the Neoproterozoic oxygenation event (NOE) is known to have been associated with glaciations. The global-scale external forcing required to switch the natural convective system to its present-day configuration is suggested to have been associated with Neoproterozoic glaciations and the subsequent lowering of ocean water salinity that accompanied them. We propose that this inverted the ocean water density gradient, allowing the oxygenation of the oceans for the first time. It is beyond the scope of this work to model the complex natural convection system, but we hope that geophysicists and numerical modellers will quantitatively evaluate the hypothesis proposed here to validate or refute our proposition.

中文翻译：

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关于太古代和元古代海洋的氧化作用

现代海洋环流表现为一个复杂的强制对流系统，其特点是水温降低，但水密度随深度增加而增加。溶解氧含量——最初由于生物需氧量而降低——也随着深度的增加而增加。与目前的情况相反，我们认为在太古宙和元古代时期，倒置剖面可能已经形成，随着深度的增加，海水温度升高，密度和溶解氧降低。这些倒置的温度和密度剖面导致古海洋环流表现为自由对流系统。有人提出，这种可能是稳定的或混乱的并受二次不稳定性影响的自由对流阻碍了古海洋的深层氧化。大氧合事件（GOE）和休伦冰期同时发生可能并非巧合，就像已知新元古代氧合事件（NOE）与冰川作用有关。将自然对流系统转变为现在的配置所需的全球范围外强迫被认为与新元古代冰川作用以及随之而来的海水盐度降低有关。我们建议这颠倒了海水密度梯度，首次允许海洋氧化。模拟复杂的自然对流系统超出了这项工作的范围，但我们希望地球物理学家和数值建模师能够定量评估这里提出的假设，以验证或反驳我们的主张。