Noble gas tracers of ventilation during deep-water formation in the Weddell Sea
Noble gas tracers of ventilation during deep-water formation in the Weddell Sea
复制标题
威德尔海深水形成期间通风的稀有气体示踪剂
DOI：
10.1088/1755-1315/35/1/012019
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
P. Heimbach
中科院分区：
文献类型：
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作者：
D. Nicholson;S. Khatiwala;P. Heimbach
为了探索深海水团形成过程中不完全的海-气平衡的动力学及其意义，我们模拟了海洋环流与气候估算(ECCO)全球海洋状态估算中的惰性气体。利用无矩阵牛顿-克雷洛夫(MFNK)格式，提出了一种新的计算方法来快速计算惰性气体示踪剂的周期季节解。MFNK允许快速计算示踪剂的循环平稳解(即旋转的、重复的季节性循环)，否则由于深海动态调整的长时间尺度(1000年S年)，这在计算上是不可行的。一套实验隔离了单独的过程，包括大气压力效应、溶解度泵和海气泡通量。除了这些模拟的过程外，还需要0.28±0.07%的冰川融水的体积贡献来协调威德尔海的深水观测。我们工作的另一个主要发现是，模型模拟中重惰性气体的饱和异常比威德尔海观测所建议的负两倍以上。这一结果表明，模型水团在俯冲之前没有足够的通风，因此在高纬度大气和海洋之间没有足够的沟通。稀有气体观测和ECCO模拟之间的差异突出表明，我们在模拟高纬度通风的方式上仍然存在重大不足，这对海洋吸收和储存碳有很大影响。
To explore the dynamics and implications of incomplete air-sea equilibration during the formation of abyssal water masses, we simulated noble gases in the Estimating the Circulation & Climate of the Ocean (ECCO) global ocean state estimate. A novel computation approach utilizing a matrix-free Newton-Krylov (MFNK) scheme was applied to quickly compute the periodic seasonal solutions for noble gas tracers. MFNK allows for quick computation of a cyclo-stationary solution for tracers (i.e., a spun-up, repeating seasonal cycle), which would otherwise be computationally infeasible due to the long time scale of dynamic adjustment of the abyssal ocean (1000’s of years). A suite of experiments isolates individual processes, including atmospheric pressure effects, the solubility pump and air-sea bubble fluxes. In addition to these modeled processes, a volumetric contribution of 0.28 ± 0.07% of glacial melt water is required to reconcile deep-water observations in the Weddell Sea. Another primary finding of our work is that the saturation anomaly of heavy noble gases in model simulations is in excess of two-fold more negative than is suggested from Weddell Sea observations. This result suggests that model water masses are insufficiently ventilated prior to subduction and thus there is insufficient communication between atmosphere and ocean at high latitudes. The discrepancy between noble gas observations and ECCO simulations highlights that important inadequacies remain in how we model high-latitude ventilation with large implications for the oceanic uptake and storage of carbon.