Gas movement through sea ice

Abstract

UNLIKE ices from pure or freshwater, sea ice is a highly permeable medium for gases. We have found that: (1) the migration of these gases along the grain boundaries (probably in brine channels) was 2 to 6 times as great as that at right angles to the principal axis of the grain boundaries; (2) the rate of penetration is ∼ 30 cm h⁻¹ at −15 °C for halogenated gases (in nl ml⁻¹ quantities) and 60 cm h⁻¹ at −7 °C for carbon dioxide (in μl ml⁻¹ quantities); (3) the vertical migration is about twice as fast as horizontal migration at −15 °C, and (4) for one experiment with a block of semi-fresh pressure ridge ice, the migration rate was ∼ 60 cm h⁻¹ at −15 °C. The permeation constants are estimated to be 10⁻⁷ cm² s⁻¹ atm⁻¹ at −15 °C for SF₆, and 2 × 10⁻⁵ cm² s⁻¹ atm⁻¹ for CO₂ at −7 °C. These data strongly indicate that gas migration through sea ice is an important factor in ocean–atmosphere winter communication particularly when the surface temperature is > −10 °C.