摘要
使用中国科学院大气物理研究所(IAP)三十层全球海洋模式(L30T63)研究了CFC-11在全球海洋中的吸收和分布,初步讨论了决定其分布特征的可能因素。该模式采用自由表面结构和Gent-McWilliams中尺度示踪物参数化方案。通过对控制试验得到的CFC-11模拟结果分析可知,CFC-11海表浓度受温度影响显著,其分布形状大致与温度相似,但梯度相反。通量的分布受温度影响很大,且表现出很明显的季节变化特征,如不饱和区一般出现在冬季海区的中层水形成处或者强对流混合存在的区域。另外,对CFC-11的模拟结果与三个大洋的五个断面航测资料做了对比,发现模拟结果与观测资料吻合较好,能比较清楚地反映CFC-11输送与等密度面垂直分布以及环流场的密切关系,如在南大洋50°S以北至35°S以南等密度面的向下加深区是CFC-11的主要贮存区等。与大多数前人的工作相比,该模拟结果较好地反映了CFC-11在南大洋的分布特征。从这些反映出该模式对于大洋十年尺度物质交换与海洋内部输送的模拟是比较准确的。
Ocean general circulation models （OGCMs） are widely used to understand the role of the ocean as a sink for greenhouse gases. To get realistic amounts of absorbed gases, it is necessary to assess the ability of ocean models simulating ocean realistic processes, especially the oceanic ventilation. Chlorofluorocarbons （CFCs） are very useful tracers for the study of oceanic ventilation on decadal timescales. As a result, many OGCMs have been used to study the oceanic uptake and storage of CFCs, including the influences of mesoscale tracer mixing scheme on the distribution of the CFCs concentration. However, a large difference still exists between the observation and simulated results of CFCs, and even between the models. To improve the ability of estimate of oceanic CFC inventories, the further research is required, including use of different models. The uptake and distribution of CFC-11 are investigated in a thirty-level global ocean general circulation model （L30T63）, which is developed by the Institute of Atmos-pheric Physics, Chinese Academy of Sciences. The model employs the free surface formulation and the Gent-McWillianas parameterization of mesoscale mixing of tracers. The possible factors that determine the features of CFC-11 distributions are preliminarily discussed in this paper. In the control numerical experiment, the model is spun up from climatological initial conditions, and it is run for 1050 years to obtain equilibration. On the basis of the 1050 years simulated results, an additional passive tracer of CFC-11 is included in the model, and the model is run for another 55 years from 1944 to 1998. CFC-11 enters the ocean by the air-sea gas exchange at the ocean surface. According to the simulated results of CFC-11 in the control numerical experiment, the distributions of CFC-11 concentrations in the ocean surface are remarkably affected by sea surface temperature. The pattern of CFC-11 distributions is similar to that of sea surface temperature, but the direction of gradient is converse. The distribution of exchange fluxes between the ocean and the atmosphere is also affected by the sea surface temperature, and shows significant seasonal variations. For example, undersaturations are usually found in the area where the intermediate water is formed or the convection is significant during the wintertime. In addition, the simulated results of CFC-11 are compared with the cruise data of five sections in three oceans. The simulated results are generally in agreement with the observations in most areas. For example, the simulated result along 24 °N in the North Atlantic Ocean clearly shows that the vertical distribution of CFC-11 in the upper ocean is much related to the local flow fields, which is also shown in the observations. In many areas the simulated results show that the transport of CFC-11 is associated with the vertical pattern of the isopycnal surfaces and with circulation features. In the Southern Ocean isopycnal surfaces are steep from 35°S to 55°S, where there is also a main storage of CFC-11. In contrast, the seawater density of the upper ocean at 10 °N is the lightest in the whole ocean, where CFC-11 concentrations are lower in comparison with those in other areas at the same depth. Compared with most of previous work by other researchers, the simulations well generate the feature of distributions of the CFC-11 concentration in the Southern Ocean. All of those reflect that the simulated exchange and transport of tracers on decadal timescales from the model are comparatively reasonable.
出处
《大气科学》
CSCD
北大核心
2006年第4期671-681,共11页
Chinese Journal of Atmospheric Sciences
基金
中国科学院知识创新工程重大项目KZCX1-SW-01-16
中国科学院"引进国外杰出人才"计划项目"全球环境变化-碳循环研究"
