Study On The Influence Of Wave Mixing On The Depth Of Mixed Layer In Southern Ocean

The surface mixed layer connects the ocean interior with the atmosphere, which directly influences the exchanges of heat, momentum, and energy between the ocean and atmosphere. Therefore the mixed layer plays an important role in the global climate system. A good understanding of the mixed layer is one of the most important variables in the global climate system. However, numerical models, including the ocean general circulation model(OGCM), coupled climate model, and Earth System Model, have deficiency in simulating the surface mixed layer.Based on the First Institute of Oceanography Earth System Model, version 1.0(FIO-ESM), two numerical experiments were established. This article is intended to focus on the effect of the wave-induced mixing in the Southern Ocean and the heat budget of the upper Southern ocean. The control run for the preindustrial period(before 1850 AD) integrates the coupled physical climate model for 1200 years, and we select model year 801-850. Only one model(FIO-ESM) among 45 includes the nonbreaking wave-induced mixing in the CMIP5 models(Huang et al., 2014). In this article, one of the control runs use the original FIO-ESM, the other one also use the FIO-ESM but turnoff the wave component. As commonly known, the ocean MLD is primarily determined by turbulent mixing processes and buoyant forcing at the air-sea interface. Compared with the results without the wave component, the nonbreaking wave-induced mixing play an important role in simulating the MLD of the Southern Ocean(35°S-65°S). It turned out that the nonbreaking wave-induced mixing can deepen the upper ocean mixed layer in the summer and shallow it in the winter. The changes in the MLD shows a seasonal cycle. In the austral summer(July-August-September), the nonbreaking wave influence the MLD by the dynamic process(enhancing the vertical mixing). The nonbreaking wave can also increase the heat of the upper ocean. The increasing of the heat can change the thermodynamic structure and influence the MLD. Therefore, the nonbreaking wave can observably influence the MLD in both summer and winter. Compared with the summer, the MLD in austral winter(January-February-March) is much deeper. The nonbreaking wave influence the MLD in the austral winter by the thermodynamic process(increasing the heat of the upper ocean). In addition, the article analyze the changes in the SST and show the mechanism of the changes in the MLD which caused by the nonbreaking wave.