Simulations of seasonal variations in carbonate parameters in Chukchi Sea 2014
Understanding the seasonal variation of air-sea CO2 exchange and the underlying mechanisms of biogeochemical dynamics is important for predicting the impacts of climate change on and feedback by the ocean. The box model simulation aims to investigate how a flexible C:N uptake ratio by phytoplankton affects DIC fixation and air-sea CO2 fluxes in the Chukchi Sea. Two scenarios with different C:N uptake ratios were examined in the box model. For the fixed-stoichiometry scenario, a C:N uptake ratio of 6.6 (Redfield ratio) was used. For the non-Redfield scenario, much higher C:N uptake ratios were used. The simulations are conducted separately for the southern Chukchi Sea (<69.5ºN) and the northern Chukchi Sea (>69.5ºN) from spring to summer in 2014. We found that a box model with a non-Redfield C:N uptake ratio can adequately reproduce observed pCO2 and DIC, which reveals that, during the intensive growing season (late spring to early summer), 30%-46% CO2 uptake in the Chukchi Sea was supported by a flexible stoichiometry of phytoplankton.
Steps to reproduce
The method of this box model simulation has been described in the related manuscript (Ouyang et al., 2022). Briefly, the initial TA and DIC values were set to the mean value of observations in the surface mixed layer in late spring, and the initial sea surface pCO2 was calculated from the initial TA and DIC using the seacarb package in R (Gattuso et al., 2018). TA in the subsequent season was linearly interpolated based on observations. For each simulation step, sea surface pCO2 was calculated from TA and DIC at the corresponding step. Ouyang, Z., Collins, A., Li, Y., Qi, D., Arrigo, K. R., Zhuang, Y., Nishino, S., Humphreys, M. P., Kosugi, N., Murata, A., Kirchman, D., Chen, L., Chen, J., Cai, W-J. 2022. Seasonal water mass evolution and non-Redfield dynamics enhance CO2 uptake in the Chukchi Sea. (under review in JGR-Oceans) Gattuso J.-P., Epitalon J.-M., Lavigne H. & Orr J., 2018. seacarb: seawater carbonate chemistry. R package version 3.2.10. http://CRAN.R-project.org/package=seacarb