Earth’s Cryosphere, 2010, Vol. XIV, No. 4, p. 17-29

ROLE OF THE ARCTIC SEA ICE COVER IN THA GAS EXCHANGE OF THE SURFACE GEOSPHERES

V.N. Golubev

Lomonosov Moscow State University, Department of Geography, 119991, Moscow, Leninskie Gory, Russia, golubev@geol.msu.ru

The CO₂ balance between the Earth surface geospheres is mainly regulated by the atmosphere–ocean gas exchange. The latter reaches dynamical equilibrium under certain relationships between the gas partial pressure and the water temperature/salinity. The sea ice extent in Arctic seas annually varies from 11–13 millions km² in March to 4–7 millions km² in September. Since the sea ice is practically impermeable for the atmospheric gases, the variability of the sea ice extent unavoidably affects the gas balance. These effects are not yet fully accounted for in the analysis and modeling of polar meteorology and global climate.
High correlation is observed between the seasonal variability of the atmospheric CO₂ content and the sea ice extent. The CO₂ content decreases in the atmosphere and its increase in the sea water takes place during the period of melting of the sea ice up to the minimal sea ice extent (June–September). The increase in the CO₂ content in the atmosphere of the Northern Hemisphere corresponds to the period of maximal development of the sea ice cover (November–April). The moments of change in the tendencies are strongly related to the near-surface monthly-mean air temperatures reaching the freezing temperature of water (ice melt). The amplitudes of the cycles increase with latitude: from 0–5 ppm at 10° S to 20 ppm at 60–80° N. This corresponds to additional flux at the interface and indicates formation of CO₂ deficit in sea waters during winter seasons.
Due to the sea ice-related seasonal cycles, the green house effect is enhanced by additional 8 ppm of CO₂ in the Northern Hemisphere, which is 2 % higher in comparison to summer seasons, respectively. The zone to the North from 60° N, where the amplitude of the seasonal change of the CO₂ content in the atmosphere reaches 20 ppm, the green house effect in winter seasons becomes 6 % higher than in summers, and partly compensates the heat losses related to seasonal cycle of incoming Solar radiation, increase of the mean surface albedo and decrease in the atmospheric content of the water vapor.

Key words: Sea ice, CO₂, climatic conditions, interannual variations, amplitude, greenhouse effect.

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