Ocean Circulation under Globally Glaciated Snowball Earth Conditions: Steady-State Solutions
Ocean Circulation under Globally Glaciated Snowball Earth Conditions: Steady-State Solutions
复制标题
DOI：
10.1175/jpo-d-13-086.1
复制
发表时间：
2014-01-01
影响因子：
3.5
通讯作者：
Tziperman, Eli
中科院分区：
文献类型：
--
作者：
Ashkenazy, Yosef;Gildor, Hezi;Tziperman, Eli
在近似7.5亿年到6.35亿年前的新元古代，地球经历了至少两次重大的、可能是全球性的冰川作用，被称为雪球地球。虽然许多研究都集中在这些事件中大气和海洋冰流的动力学和作用，但只有少数研究了相关的海洋环流，没有研究探讨过由地热通量驱动的厚（约1公里深）海冰覆盖下的海洋环流。在这里，一个厚海冰流模式耦合到海洋环流模式被用来研究雪球地球条件下的海洋环流。首先在一个简化的纬向对称假设下研究了海洋环流，发现（i）强赤道纬向急流和（ii）强纬向翻转环流圈，仅限于非常靠近赤道的区域。本文导出了纬深海洋动力学的解析近似，发现纬向翻转环流圈的大小只取决于水平涡动粘性和Coriolis参数随纬度的变化。解析近似地再现了数值结果。三维海洋模拟，重建新元古代大陆配置，确认纬向对称动力学，并显示额外的边界电流和强大的上升流和下降流附近的大陆。
Between similar to 750 and 635 million years ago, during the Neoproterozoic era, the earth experienced at least two significant, possibly global, glaciations, termed Snowball Earth. While many studies have focused on the dynamics and the role of the atmosphere and ice flow over the ocean in these events, only a few have investigated the related associated ocean circulation, and no study has examined the ocean circulation under a thick (similar to 1 km deep) sea ice cover, driven by geothermal heat flux. Here, a thick sea ice-flow model coupled to an ocean general circulation model is used to study the ocean circulation under Snowball Earth conditions. The ocean circulation is first investigated under a simplified zonal symmetry assumption, and (i) strong equatorial zonal jets and (ii) a strong meridional overturning cell are found, limited to an area very close to the equator. The authors derive an analytic approximation for the latitude-depth ocean dynamics and find that the extent of the meridional overturning circulation cell only depends on the horizontal eddy viscosity and (the change of the Coriolis parameter with latitude). The analytic approximation closely reproduces the numerical results. Three-dimensional ocean simulations, with reconstructed Neoproterozoic continental configuration, confirm the zonally symmetric dynamics and show additional boundary currents and strong upwelling and downwelling near the continents.