The effect of biological activity, CaCO₃ mineral dynamics, and CO₂ degassing in the inorganic carbon cycle in sea ice in late winter‐early spring in the Weddell Sea, Antarctica

Abstract

[1] A large-scale geographical study of the ice pack in the seasonal ice zone of the Weddell Sea, Antarctica, took place from September to October 2006. Sea ice brines with a salinity greater than 58 and temperature lower than À3.6 C were sampled from 22 ice stations. The brines had large deficits in total alkalinity and in the concentrations of the major dissolved macronutrients (total dissolved inorganic carbon, nitrate, and soluble reactive phosphorus) relative to their concentrations in the surface oceanic water and conservative behavior during seawater freezing. The concentration deficits were related to the dissolved inorganic carbon-consuming processes of photosynthesis, CaCO 3 precipitation, and CO 2 degassing. The largest concentration deficits in total dissolved inorganic carbon were found to be associated with CaCO 3 precipitation and CO 2 degassing, because the magnitude of the photosynthesis-induced concentration deficit in total dissolved inorganic carbon is controlled by the size of the inorganic nutrient pool, which can be limited in sea ice by its openness to exchange with the surrounding oceanic water.

Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic

“…This biological effect on T CO 2 is probably limited to the very bottom decaying section of the sea ice cover Glud et al, 2014). This is similar to what has been described in the Beaufort Sea (Arctic, Geilfus et al, 2012b) and in the Weddell Sea (Antarctica, Papadimitriou et al, 2012) on landfast sea ice, although during early spring, i.e., at ice temperatures colder than those observed during the present study. Therefore sea ice and brine samples from these other studies are located on the other side of the seawater value, i.e., lying between the precipitation of calcium carbonate and the release of CO 2 , in the nTA / nT CO 2 space.…”

CO<sub>2</sub> and CH<sub>4</sub> in sea ice from a subarctic fjord under influence of riverine input

“…Other processes affect the pCO 2 concentrations within sea ice such as the precipitation and dissolution of calcium carbonate Geilfus et al, 2012bGeilfus et al, , 2013aPapadimitriou et al 2007Papadimitriou et al , 2012Rysgaard et al, 2007Rysgaard et al, , 2011Rysgaard et al, , 2013. During the sea-ice melt, the carbonate dissolution promotes lower pCO 2 conditions (Rysgaard et al, 2011).…”

“…Finally, primary production as well bacterial respiration can affect the inorganic carbon dynamics within sea ice (Delille et al, 2007;Kaartokalio et al, 2013;Papadimitriou et al 2012;Rysgaard et al, 2007Rysgaard et al, , 2009Søgaard et al, 2013). Ice melting through spring and summer will produce both a continuous reduction of the bulk ice pCO 2 and an increase of the ice permeable features leading to pCO 2 sub-saturated sea ice relative to the atmosphere and hereby enhance the air-sea flux of CO 2 .…”

Ikaite crystal distribution in winter sea ice and implications for CO<sub>2</sub> system dynamics

“…There is urgency for increasing the knowledge base, given that the precipitation of CaCO 3 is implicated in many processes of global significance, including the sea ice-driven carbon pump and global carbon cycle (Delille et al, 2007;Papadimitriou et al, 2012) and pH conditions (acidification) in surface waters (Rysgaard et al, 2012;Hare et al, 2013). Quantification of CaCO 3 crystals in sea ice in the few previous studies has been made on melted samples assuming that ikaite will not dissolve if temperature is maintained below 4 • C. In principle, however, dissolution may also be related to the reaction of ikaite with CO 2 in the meltwater or with the atmosphere during the melting procedure, which can last for days at low temperature allowing the possibility of changing pH in the surroundings of the ikaite crystal and underestimation of ikaite concentration.…”