A Model‐Based Analysis of Physical and Biogeochemical Controls on Carbon Exchange in the Upper Water Column, Sea Ice, and Atmosphere in a Seasonally Ice‐Covered Arctic Strait

Abstract

AbstractIn this study, we consider a 1‐D model incorporating both sea ice and pelagic systems in order to assess the importance of various processes on the vertical transport and exchange of carbon in the seasonally ice‐covered marine Arctic. The model includes a coupled ice‐ocean ecosystem, a parameterization of ikaite precipitation and dissolution, a formulation for ice‐air carbon exchange, and a formulation for brine rejection and freshwater dilution of dissolved inorganic carbon (DIC) and total alkalinity (TA) associated with ice growth and melt. Sensitivity analyses illustrate that (1) the pelagic ecosystem accounts for more than half of the net ocean carbon uptake, but ice algae have little effect on the air‐sea exchange in the standard run; (2) inclusion of ikaite precipitation and dissolution do not strongly affect the net ocean carbon uptake for concentrations within the observed range but can become important for larger concentrations; (3) varying DIC and TA in the ice by equal amounts, or varying brine deposition depth, does not affect the net ocean carbon uptake, because the coincident changes in TA and DIC concentrations at the sea surface serve to counteract one another with respect to sea surface pCO2; and (4) the proportions of carbon released to the water column (versus to the atmosphere) during ice growth and melt are important quantities to constrain in order to determine the contribution of the combined ice‐ocean system to oceanic uptake of atmospheric carbon.