Modeling evidences for global warming, Arctic seawater freshening, and sluggish oceanic circulation during the Early Toarcian anoxic event
Modeling evidences for global warming, Arctic seawater freshening, and sluggish oceanic circulation during the Early Toarcian anoxic event
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DOI：
10.1029/2012pa002283
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发表时间：
2012-06-13
期刊：
影响因子：
--
通讯作者：
Donnadieu, Yannick
中科院分区：
文献类型：
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作者：
Dera, Guillaume;Donnadieu, Yannick
在早期Toarcian变暖事件（1.83亿年前）期间记录的古生态干扰，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，通常被认为是地球对超级温室条件快速出现的可能反应的过去例子。然而，物理机制解释全球和当地的古环境事件的表现仍然是高度争论。在这里，我们分析了古气候和古海洋学的后果，在多尺度分辨率的大气pCO（2）水平的增加，使用一个完全耦合的海洋-大气模式（FOAM）。我们发现，与更强的高纬度降水率和增强的大陆径流，消亡的极地海冰由于全球变暖事件涉及北极表面海水的区域清新。这些扰动导致全球海洋环流的逐渐减缓，造成深海和陆缘盆地广泛的海洋分层和海底缺氧过程。在协议非常负的氧同位素值从西北特提斯的化石贝壳测量，我们的模拟还表明，经常性排放的咸和营养丰富的北极表面沃茨通过维京海盗走廊可能导致在西北特提斯海的盐度和海水三角洲O-18的垂直和地理梯度。当地的对比条件下，水质量密度和生产率的上升，由于强大的营养供应，可以部分解释区域严重的缺氧事件的限制欧洲北部域，因为它已经建议和模拟区域。
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 delta O-18 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.