17:15 〜 18:45
[ACG41-P05] Impacts of vertical mixing and heating exchange on air-sea CO2 flux in the tropical Pacific
キーワード：Air-sea CO2 Exchange, Vertical Mixing, Light Penetration Depth, Tropical Pacific
The tropical Pacific plays an important role in the global carbon cycle due to its significant CO2 outgassing and large influence on the interannual variability of global ocean-atmosphere CO2 fluxes. However, many large-scale models have difficulties in reproducing the spatial-temporal variability of observed ocean pCO2 in the tropical Pacific, with implications for the estimates of air-sea CO2 exchange. Here, we employed a basin-scale model that generally reproduced the spatial pattern of ocean pCO2, but overestimated ocean pCO2 in the upwelling region of the tropical Pacific. Given that the tropical Pacific was a DIC-driven system, the overestimated pCO2 in the east was probably caused by “too strong” vertical mixing in our model parameterization. To address this issue, we tested different parameterization with reduced vertical mixing. Moreover, the previous version of the model applied a constant value for light penetration depth, which could cause biases on heat exchange thus on vertical mixing. Therefore, our experiments also included the simulations with variable light penetration depth (a function of chlorophyll and particle concentrations), which showed improvement in DIC fields in the upwelling region (i.e., a decrease of DIC). The sensitivity experiments demonstrated that reduced vertical mixing caused a significant decrease of DIC and thus improved simulation of pCO2 in most sections of tropical Pacific. Our study indicated the importance of vertical mixing (and heating exchange) on variation of air-sea CO2 exchange in the tropical Pacific.