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首页> 外文期刊>Paleoceanography >Modeling evidences for global warming, Arctic seawater freshening, and sluggish oceanic circulation during the Early Toarcian anoxic event (Review)
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Modeling evidences for global warming, Arctic seawater freshening, and sluggish oceanic circulation during the Early Toarcian anoxic event (Review)

机译：在早期Toarcian缺氧事件中模拟全球变暖，北极海水淡化和海洋环流缓慢的证据（综述）

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摘要

The paleoecological disturbances recorded during the Early Toarcian warming event (183 Myr ago), including marine anoxia, sea level rise, seawater acidification, carbonate production crisis, and species extinctions, are often regarded as past examples of Earth's possible responses to the rapid emergence of super greenhouse conditions. However, physical mechanisms explaining both the global and local expressions of paleoenvironmental events are still highly debated. Here we analyze the paleoclimatic and paleoceanographic consequences of increases in atmospheric pCO _2 levels at a multiscale resolution using a fully coupled ocean-atmosphere model (FOAM). We show that, in association with stronger high-latitude precipitation rates and enhanced continental runoff, the demise of polar sea ice due to the global warming event involved a regional freshening of Arctic surface seawaters. These disturbances lead to progressive slowdowns of the global oceanic circulation accountable for widespread ocean stratification and bottom anoxia processes in deep oceanic settings and epicontinental basins. In agreement with very negative oxygen isotope values measured on fossil shells from the NW Tethys, our simulations also show that recurrent discharges of brackish and nutrient-rich Arctic surface waters through the Viking Corridor could have led to both vertical and geographical gradients in salinity and seawater δ ~(18)O in the NW Tethyan seas. Locally contrasted conditions in water mass density and rises in productivity rates due to strong nutrient supplies could partly explain the regional severity of the anoxic event in the restricted Euro-boreal domains, as it has been previously suggested and modeled regionally.
机译：在早期的Toarcian变暖事件（183 Myr以前）中记录的古生态扰动，包括海洋缺氧，海平面上升，海水酸化，碳酸盐生产危机和物种灭绝，通常被视为地球对快速崛起的可能反应的过去例子。超级温室条件。然而，解释古环境事件的整体和局部表达的物理机制仍受到高度争议。在这里，我们使用完全耦合的海洋-大气模型（FOAM），以多尺度分辨率分析了大气pCO _2水平增加的古气候和古海洋学后果。我们表明，与更强的高纬度降水率和更大的大陆径流相关联，由于全球变暖事件导致的极地海冰消亡涉及北极表层海水的区域性新鲜化。这些扰动导致全球海洋环流的逐渐减慢，这是造成深海环境和上陆盆地中广泛的海洋分层和底部缺氧过程的原因。与西北特提斯州化石壳上测得的非常负的氧同位素值相符，我们的模拟还表明，通过维京走廊反复排放咸淡和营养丰富的北极地表水可能导致盐度和海水的垂直和地理梯度变化西北特提斯海中的δ〜（18）O。如先前在区域中建议和建模的那样，由于大量养分的供应，水质密度的局部差异条件和生产率的提高可以部分解释缺氧事件在受限的欧洲北部地区的区域严重性。

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