Abstract: The Arctic sea ice-melt pond system is a key component of the Earth system. Melt ponds occur in spring and summer, and accounts for more than 30% of the sea ice surface. Carbonate systems of sea ice and melt ponds are important components of the high-latitude oceanic CO₂ budget. However, the carbon cycle and carbonate system in the melt ponds remain largely unknown. Here we review the current research on the carbonate systems and carbon sink of sea ice and melt ponds. Sea ice and melt ponds undergo similar seasonal changes each year. The enhanced primary production and dissolution of calcium carbonate crystals at the beginning of the melting season promote the strong decline of total alkalinity (TA), dissolved inorganic carbon (DIC) and CO₂ partial pressure (pCO₂) in sea ice and melt water, while the carbonate system of brineis are mainly controlled by infiltration of melt water. As the melting season advances, air-sea CO₂ exchange is promoted and pCO₂ of melt water gradually increases because of CO₂ exchange with the atmosphere; it fluctuates between zero and atmospheric level until the seasonal sea ice has completely melted. Sea ice melt ponds system can absorb approximately 10.4 Tg of carbon in one year. We identify urgent scientific questions and future research directions with respect to the carbonate systems of sea ice and melt pond.

Key words: Arctic Ocean, sea ice, melt ponds, CO₂ (carbon dioxide), carbonate system