Analysis of the Seasonal and Interannual Variations of Air-Sea CO2 Flux in the Chukchi Sea Using a Coupled Ocean-Sea Ice-Biogeochemical Model

Understanding the responses of air-sea carbon dioxide (CO2) flux to rapid environmental changes in the highly productive Chukchi Sea is of great significance for the climate prediction in the Arctic Ocean. Through analyzing the 1998-2015 hindcast simulation of a coupled ocean-sea ice-biogeochemical model, this study identifies that the key factors influencing oceanic carbon uptake in the Chukchi Sea vary seasonally. The effects of these seasonal carbon uptakes on the total annual carbon sink vary at different timescales. The model solution suggests that the Chukchi Sea acts as a perennial carbon sink of atmospheric CO2 with the annual mean influx of -3.73 +/- 3.90 mmol m(-2) d(-1). Quantitative analyses reveal that the sea ice concentration predominates the annual cycle of air-sea CO2 flux, while primary production and wind speed strengthen the capacity for carbon uptake during June-July (melt season) and October-December (freeze season), respectively. The total annual carbon sink shows an increasing trend during 1998-2015 with a multi-year average of 9.22 +/- 1.93 Tg C y(-1). The carbon uptakes during June-July and August-September (open water season), which are respectively regulated by primary production and open water area at interannual scale, present significant long-term increases and jointly determine the secular increase trend of the total annual carbon sink. Interannual CO2 absorption during the freeze season is sensitive to the sea ice concentration and wind conditions, presenting the greatest year-to-year variation but insignificant long-term trend, and modulates the interannual amplitude of the total annual carbon sink.

Automated summary

The study reveals that the oceanic carbon uptake in the Chukchi Sea is influenced by seasonal factors with varying impacts on the total annual carbon sink. The model suggests that the Chukchi Sea serves as a perennial carbon sink of atmospheric CO2. Factors such as sea ice concentration, primary production, and wind speed play significant roles in influencing the air-sea CO2 flux in different seasons.