二维温盐环流模式研究^(14)C在海洋中的分布

A Study of the Distribution of 14 C in the Ocean Using a Two Dimensional Thermohaline Circulation Model

海洋碳循环模式中常使用放射性同位素１４Ｃ来检验该模式的物理模型是否较好地反映了海洋中的大尺度变化的过程。本工作使用的物理模型是包括太平洋、大西洋和南大洋在内的二维温盐环流模式，在给定的年平均海表强迫下积分４０００年后，环流达到准稳态，其定常流场用来驱动１４Ｃ模式。对１４Ｃ模式积分５０００年以上，可得到１４Ｃ稳态的分布。使用不同的二氧化碳海气交换系数和垂直湍流扩散系数值进行了７个实验，发现使用Ｂｒｏｅｃｋｅｒ等的交换系数方程和扩散系数值依深度从０．６增加到１．４５ｃｍ２·ｓ－１，模拟的结果较好。使用观测到的大气中１４Ｃ含量，进一步研究了工业革命后及核试验后的１４Ｃ在海洋中的穿透，模拟结果与现有的一些资料进行了比较。

Oceanic carbon models often use radiocarbon to test the performance of the physical model for the large scale processes in the oceans. The physical model used in this work is a two dimensional thermohaline circulation model, including the Pacific, the Atlantic and the Southern Ocean. Under the forcing of given yearly mean temperature and salinity at the surface, the model is integrated over 4000 years to reach a quasi steady state. A constant flow field is used to drive tracer radiocarbon for the integration of over 5000 years until a steady state is reached. Seven numerical experiments are conducted by altering the values of vertical turbulent diffusivity and of the exchange coefficient of carbon dioxide between the atmosphere and the ocean. Using an exchange coefficient from Broecker et al.'s equation and the depth dependent vertical turbulent diffusivity which varies from 0.6 cm 2 ·s 1 at the surface to 1.45 cm 2·s 1 at the bottom layer, the modelled results are better. Using the observed time history of atmospheric radiocarbon content, the penetration of radiocarbon in the ocean is futher studied after industrialization and the test of nuclear weapons. The modelled results are compared with some observations, providing a reasonable agreement.