HR: 0800h
AN: C51B-0399    [Abstracts]
TI: The Physico-chemical Effects of Sea Ice on Ocean Surface pCO2 and Atmospheric Flux in Antarctica
AU: * Loose, B
EM: brice@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Takahashi, T
EM: takahashi@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Ho, D
EM: david@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AU: Schlosser, P
EM: schlosser@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AB: Sea ice impedes gas exchange between atmosphere and ocean, however sea ice formation itself concentrates all solutes, including gases, in the brine pockets that form within the ice. As well as solute rejection, several physicochemical factors conspire to elevate the CO₂ concentration in the liquid brine: (1) as salinity increases the gas solubility decreases, (2) bicarbonate dissociates in favor of CO₂ concentration and (3) calcium carbonate can precipitate, decreasing alkalinity. Brine with a high concentration of CO₂ may vent gas to the atmosphere or convey that excess gas (relative to atmospheric equilibrium) to the water column through gravity-driven brine drainage. In Antarctica, winter mixing transports Circumpolar Deep Water into the mixed layer, bringing heat and excess CO₂ into contact with the base of the sea ice. We explore these effects on CO₂ concentration using a one-dimensional model of sea ice formation, brine drainage and the equilibrium kinetics of the seawater carbonate system as an approximation for CO₂ in brine. The eventual fate of excess CO₂ in sea ice depends on the ice permeability, but may also be regulated by light and salt adapted algal communities that are most dense in the lower 20 cm of the ice.
DE: 0428 Carbon cycling (4806)
DE: 0750 Sea ice (4540)
DE: 1009 Geochemical modeling (3610, 8410)
SC: Cryosphere [C]
MN: 2007 Fall Meeting