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Sea ice is an active source or a sink for carbon dioxide (CO₂), although to what extent is not clear. Here, we analyze CO₂ dynamics within sea ice using a one-dimensional halothermodynamic sea ice model including gas physics and carbon biogeochemistry. The ice-ocean fluxes, and vertical transport, of total dissolved inorganic carbon (DIC) and total alkalinity (TA) are represented using fluid transport equations. Carbonate chemistry, the consumption, and release of CO₂ by primary production and respiration, the precipitation and dissolution of ikaite (CaCO₃·6H₂O) and ice-air CO₂ fluxes, are also included. The model is evaluated using observations from a 6 month field study at Point Barrow, Alaska, and an ice-tank experiment. At Barrow, results show that the DIC budget is mainly driven by physical processes, wheras brine-air CO₂ fluxes, ikaite formation, and net primary production, are secondary factors. In terms of ice-atmosphere CO₂ exchanges, sea ice is a net CO₂ source and sink in winter and summer, respectively. The formulation of the ice-atmosphere CO₂ flux impacts the simulated near-surface CO₂ partial pressure (pCO₂), but not the DIC budget. Because the simulated ice-atmosphere CO₂ fluxes are limited by DIC stocks, and therefore <2 mmol m⁻² d⁻¹, we argue that the observed much larger CO₂ fluxes from eddy covariance retrievals cannot be explained by a sea ice direct source and must involve other processes or other sources of CO₂. Finally, the simulations suggest that near-surface TA/DIC ratios of ∼2, sometimes used as an indicator of calcification, would rather suggest outgassing.

Item Type:	Refereed Article
Keywords:	CO2, ikaite, sea ice, model
Research Division:	Earth Sciences
Research Group:	Oceanography
Research Field:	Biological oceanography
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the mathematical sciences
UTAS Author:	Moreau, S (Dr Sebastien Moreau)
ID Code:	109563
Year Published:	2015
Web of Science® Times Cited:	20
Deposited By:	Ecology and Biodiversity
Deposited On:	2016-06-22
Last Modified:	2017-10-31
Downloads:	140 View Download Statistics