Abstract: Sea ice retreat in the Arctic Ocean has caused an increase in open water area, which has consequently contributed to the absorption of more carbon dioxide (CO₂) by surface seawater, and an increase in the partial pressure of CO₂ (pCO₂). However, there is a lack of research on the dramatic changes in pCO₂ during sea ice retreat and its interaction with sea ice. Based on the 3rd Chinese National Arctic Research Expedition data in 2008, this study found that the distribution of summer sea surface pCO₂ in the western Arctic Ocean was characterized by low values on the shelf and high values in the ocean basin. The study area overall was a sink for atmospheric CO₂, with air-sea CO₂ fluxes of 13.8 mmol·m^–2·d^–1 in the shelf area and 3.7 mmol·m^–2·d^–1 in the basin. This study used a mass balance model to investigate the response of sea surface pCO₂ in the Canadian Basin during the whole period of sea ice melting process. The results showed that: (1) during the melting process, pCO₂ slowly increased by air-sea CO₂ exchange; (2) after the sea ice had completely melted and with prolonged exposure of the sea surface to the air, the combined effects of air-sea CO₂ exchange and warming resulted in a rapid increase in pCO₂, and the rate of increase was higher than that in the melting stage.

Key words:

western Arctic Ocean, pCO_2,  sea surface temperature, air-sea exchange, net primary productivity