Oceanic Uptake of Oxygen During Deep Convection Events Through Diffusive and Bubble‐Mediated Gas Exchange
Oceanic Uptake of Oxygen During Deep Convection Events Through Diffusive and Bubble‐Mediated Gas Exchange
复制标题
深对流事件期间海洋通过扩散和气泡介导的气体交换吸收氧气
DOI：
10.1002/2017gb005716
复制
发表时间：
2017
影响因子：
5.2
通讯作者：
A. Bracco
中科院分区：
文献类型：
--
作者：
Daoxun Sun;T. Ito;A. Bracco
溶解氧（O2）的浓度在整个海洋的各种化学和生物过程中起着重要作用。物理供给和生物消耗之间的平衡控制着海洋内部的O2水平，而O2向深层沃茨的供给只能通过极地海洋的深层对流来实现。我们开发了一个理论框架，描述了开放海洋深对流事件期间的海洋O2吸收，并对一套数值敏感性实验进行了测试。我们的框架允许两个预测，证实了数值模拟。首先，冬季冷却的持续时间和强度都对给定浮力损失的总O2吸收有贡献。更强的冷却导致更深的对流，并且氧化可以到达更深的深度。较长的冷却期的持续时间增加了对流季节的O2吸收总量。其次，气泡介导的O2流入倾向于通过将O2的气-海不平衡向过饱和转变来削弱扩散流入。扩散和气泡介导的气体交换之间的补偿程度取决于测量海洋垂直混合的相对强度和气体传输速度的无量纲数。强对流混合，这可能会发生在强冷却，减少补偿的程度，使两个组成部分的气体交换一起驱动异常强大的海洋O2吸收。
The concentration of dissolved oxygen (O2) plays fundamental roles in diverse chemical and biological processes throughout the oceans. The balance between the physical supply and the biological consumption controls the O2 level of the interior ocean, and the O2 supply to the deep waters can only occur through deep convection in the polar oceans. We develop a theoretical framework describing the oceanic O2 uptake during open‐ocean deep convection events and test it against a suite of numerical sensitivity experiments. Our framework allows for two predictions, confirmed by the numerical simulations. First, both the duration and the intensity of the wintertime cooling contribute to the total O2 uptake for a given buoyancy loss. Stronger cooling leads to deeper convection and the oxygenation can reach down to deeper depths. Longer duration of the cooling period increases the total amount of O2 uptake over the convective season. Second, the bubble‐mediated influx of O2 tends to weaken the diffusive influx by shifting the air‐sea disequilibrium of O2 toward supersaturation. The degree of compensation between the diffusive and bubble‐mediated gas exchange depends on the dimensionless number measuring the relative strength of oceanic vertical mixing and the gas transfer velocity. Strong convective mixing, which may occur under strong cooling, reduces the degree of compensation so that the two components of gas exchange together drive exceptionally strong oceanic O2 uptake.