Carbon dynamics in sea ice: A winter flux time series

A winter time series of the inorganic carbon system above, within, and beneath the landfast sea ice of the southern Beaufort Sea confirmed that sea ice is an active participant in the carbon cycle of polar waters. Eddy covariance measurements above the ice identified significant vertical CO2 fluxes, mostly upward away from the ice but with short periods of downward fluxes as well. A novel, in situ method revealed extremely high pCO(2) values within the ice that are not inconsistent with theory. The total carbon content of the ice increased slightly through the winter season, and increasing variability in the vertical profiles as spring began indicated that the inorganic carbon became mobile as the ice began to melt. During early winter, as the ice formed, inorganic carbon concentrations in the surface waters increased dramatically, along with salinity, partly because of rejection from the ice and partly from advective mixing. Brine drainage was apparently not sufficient to initiate convection, and the excess carbon remained in the surface waters into the summer.