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First estimates of the contribution of CaCO 3 precipitation to the release of CO 2 to the atmosphere during young sea ice growth
Author(s) -
Geilfus N.X.,
Carnat G.,
Dieckmann G. S.,
Halden N.,
Nehrke G.,
Papakyriakou T.,
Tison J.L.,
Delille B.
Publication year - 2013
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2012jc007980
Subject(s) - sea ice , precipitation , atmosphere (unit) , solubility , ice core , sea ice growth processes , brine , alkalinity , carbon dioxide , salinity , mineralogy , arctic ice pack , chemistry , analytical chemistry (journal) , geology , environmental chemistry , sea ice thickness , oceanography , meteorology , geography , organic chemistry
We report measurements of pH, total alkalinity, air‐ice CO 2 fluxes (chamber method), and CaCO 3 content of frost flowers (FF) and thin landfast sea ice. As the temperature decreases, concentration of solutes in the brine skim increases. Along this gradual concentration process, some salts reach their solubility threshold and start precipitating. The precipitation of ikaite (CaCO 3 .6H 2 O) was confirmed in the FF and throughout the ice by Raman spectroscopy and X‐ray analysis. The amount of ikaite precipitated was estimated to be 25 µmol kg −1 melted FF, in the FF and is shown to decrease from 19 to 15 µmol kg −1 melted ice in the upper part and at the bottom of the ice, respectively. CO 2 release due to precipitation of CaCO 3 is estimated to be 50 µmol kg −1 melted samples. The dissolved inorganic carbon (DIC) normalized to a salinity of 10 exhibits significant depletion in the upper layer of the ice and in the FF. This DIC loss is estimated to be 2069 µmol kg −1 melted sample and corresponds to a CO 2 release from the ice to the atmosphere ranging from 20 to 40 mmol m −2 d −1 . This estimate is consistent with flux measurements of air‐ice CO 2 exchange. Our measurements confirm previous laboratory findings that growing young sea ice acts as a source of CO 2 to the atmosphere. CaCO 3 precipitation during early ice growth appears to promote the release of CO 2 to the atmosphere; however, its contribution to the overall release by newly formed ice is most likely minor.