SIMULATION OF CFC-11 DISTRIBUTION BASED ON THE GLOBAL OCEANIC CARBON CYCLE MODEL MOM4 L40 AND AN ASSESSMENT OF ITS VENTILATION CAPABILITY

Abstract

CFC-11 is an important tool used to assess oceanic cycle models. The CFC-11 which is dissolved in seawater can be used to analyze the ventilation of the oceans. In this study, a tracer CFC-11 module was developed based on the global oceanic carbon cycle circulation model MOM4 L40, which was developed by the National Climate Center of China Meteorological Administration. Then, the model was employed to study the distribution of CFC-11 in the global oceans, and also to assess the model's ventilation capacity. The simulated parameters, such as the global sea surfaces' CFC-11 concentrations, inventory, vertical penetration depths, and concentration distributions, were verified against the actual observations. The results showed that the model reasonably simulated the surface and vertical distribution of the CFC-11. The main storage areas of the CFC-11 were determined to be located in the Northwest Atlantic Ocean, subtropical North Pacific Ocean, and the Southern Ocean. The distributions of the CFC-11 concentrations on the oceanic surfaces were found to be remarkably affected by the sea surfaces' temperatures. The distribution of the simulated CFC-11 was found to have a high agreement with that of the actual observations, and showed an opposite gradient to the sea surfaces' temperatures. When compared with the observations of five sections located in three oceans, the simulated results of the CFC-11 were in general agreement with the observations in the majority of the areas. In addition, the distribution of the simulated CFC-11 was found to be in agreement with meridional overturning circulation in the global oceans, and an improved simulation of the Southern Ocean and deep oceans, as well as the penetration depths, were achieved. However, there were some deviations observed between the observations and simulations. For example, in the North Atlantic Ocean, where a main storage of the CFC-11 was located, the model underestimated the absorption of the CFC-11, which was found to be related to the over-transport simulations from the high latitudes to the low latitudes. These results may have been influenced by the thermohaline circulation and forced data. Overall, it was determined that the MOM L40 reasonably simulated the absorption of the total CFC-11 in the oceans, and effectively reproduced the oceans' ventilation capabilities by simulating the passive tracer CFC-11.