FREZCHEM: A geochemical model for cold aqueous solutions

Marion, G. M.; Мироненко, М. В.; Roberts, Morien W.

doi:10.1016/j.cageo.2009.06.004

Cited by 85 publications

(75 citation statements)

References 19 publications

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“…Understanding the dynamics of those processes is an important objective for future studies. Here, we note that higher concentrations of ikaite in surface sea ice are predicted by the FREZCHEM model (Marion et al, 2010). (Fig.…”

Section: Spatial and Temporal Variability Of Ikaite Occurrence And Comentioning

confidence: 55%

“…It should be noted that FREZCHEM modeling is based on the assumption that chemical species in the sea ice environment (ice, brine, and air) have reached thermodynamic equilibrium, and that most of the thermodynamic constants used in the model were extrapolated to low temperatures rather than being directly determined experimentally. Nevertheless, the model has shown promising applications in exploring cold geochemical processes associated with seawater freezing among many others (Marion et al, 1999(Marion et al, , 2010.…”

Section: Frezchem Modelingmentioning

confidence: 99%

“…The production of ikaite in the sea ice cores was modeled by FREZCHEM (version 10), an equilibrium chemical thermodynamic model parameterized for concentrated solutions (up to 20 mol kg −1 (H 2 O)) and sub-zero temperatures (to −70 • C) (Marion et al, 2010). The model uses the Pitzer approach correcting for activity coefficients of solutes in concentrated solutions.…”

Section: Frezchem Modelingmentioning

confidence: 99%

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

et al. 2013

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Abstract. The precipitation of ikaite (CaCO 3 ·6H 2 O) in polar sea ice is critical to the efficiency of the sea ice-driven carbon pump and potentially important to the global carbon cycle, yet the spatial and temporal occurrence of ikaite within the ice is poorly known. We report unique observations of ikaite in unmelted ice and vertical profiles of ikaite abundance and concentration in sea ice for the crucial season of winter. Ice was examined from two locations: a 1 m thick land-fast ice site and a 0.3 m thick polynya site, both in the Young Sound area (74 • N, 20 • W) of NE Greenland. Ikaite crystals, ranging in size from a few µm to 700 µm, were observed to concentrate in the interstices between the ice platelets in both granular and columnar sea ice. In vertical sea ice profiles from both locations, ikaite concentration determined from image analysis, decreased with depth from surface-ice values of 700-900 µmol kg −1 ice (∼25 × 10 6 crystals kg −1 ) to values of 100-200 µmol kg −1 ice (1-7 × 10 6 crystals kg −1 ) near the sea ice-water interface, all of which are much higher (4-10 times) than those reported in the few previous studies. Direct measurements of total alkalinity (TA) in surface layers fell within the same range as ikaite concentration, whereas TA concentrations in the lower half of the sea ice were twice as high. This depth-related discrepancy suggests interior ice processes where ikaite crystals form in surface sea ice layers and partly dissolve in layers below. Melting of sea ice and dissolution of observed concentrations of ikaite would result in meltwater with a pCO 2 of <15 µatm. This value is far below atmospheric values of 390 µatm and surface water concentrations of 315 µatm. Hence, the meltwater increases the potential for seawater uptake of CO 2 .

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Section: Spatial and Temporal Variability Of Ikaite Occurrence And Comentioning

confidence: 55%

Section: Frezchem Modelingmentioning

confidence: 99%

Section: Frezchem Modelingmentioning

confidence: 99%

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

et al. 2013

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“…Ikaite precipitation in sea ice was modeled by FREZCHEM (version 13.3), an equilibrium chemical thermodynamic model parameterized for concentrated solutions (up to 20 mol kg −1 (H 2 O)) and subzero temperatures (down to −70 • C) (Marion and Kargel, 2008;Marion et al, 2010). The model uses the Pitzer approach to correct for activity coefficients of solutes in concentrated solutions.…”

Section: Frezchem Modelingmentioning

confidence: 99%

“…In addition, we employed the FREZCHEM model (Marion et al, 2010) to calculate theoretical equilibrium ikaite concentrations as a function of different sea ice temperatures in Sea-ice Environmental Research Facility (SERF) seawater with different pCO 2 values. Finally, we discuss our findings in relation to CO 2 system dynamics in sea-ice-covered seas.…”

Section: Introductionmentioning

confidence: 99%

Temporal dynamics of ikaite in experimental sea ice

et al. 2014

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Abstract. Ikaite (CaCO 3 ·6H 2 O) is a metastable phase of calcium carbonate that normally forms in a cold environment and/or under high pressure. Recently, ikaite crystals have been found in sea ice, and it has been suggested that their precipitation may play an important role in air-sea CO 2 exchange in ice-covered seas. Little is known, however, of the spatial and temporal dynamics of ikaite in sea ice. Here we present evidence for highly dynamic ikaite precipitation and dissolution in sea ice grown at an outdoor pool of the Sea-ice Environmental Research Facility (SERF) in Manitoba, Canada. During the experiment, ikaite precipitated in sea ice when temperatures were below −4 • C, creating three distinct zones of ikaite concentrations: (1) a millimeter-to-centimeter-thin surface layer containing frost flowers and brine skim with bulk ikaite concentrations of > 2000 µmol kg −1 , (2) an internal layer with ikaite concentrations of 200-400 µmol kg −1 , and (3) a bottom layer with ikaite concentrations of < 100 µmol kg −1 . Snowfall events caused the sea ice to warm and ikaite crystals to dissolve. Manual removal of the snow cover allowed the sea ice to cool and brine salinities to increase, resulting in rapid ikaite precipitation. The observed ikaite concentrations were on the same order of magnitude as modeled by FREZCHEM, which further supports the notion that ikaite concentration in sea ice increases with decreasing temperature. Thus, varying snow conditions may play a key role in ikaite precipitation and dissolution in sea ice. This could have a major implication for CO 2 exchange with the atmosphere and ocean that has not been accounted for previously.

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Gypsum crystals observed in experimental and natural sea ice

Geilfus

Galley

Cooper

et al. 2013

Geophysical Research Letters

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[1] Although gypsum has been predicted to precipitate in sea ice, it has never been observed. Here we provide the first report on gypsum precipitation in both experimental and natural sea ice. Crystals were identified by X-ray diffraction analysis. Based on their apparent distinguishing characteristics, the gypsum crystals were identified as being authigenic. The FREeZing CHEMistry (FREZCHEM) model results support our observations of both gypsum and ikaite precipitation at typical in situ sea ice temperatures and confirms the "Gitterman pathway" where gypsum is predicted to precipitate. The occurrence of authigenic gypsum in sea ice during its formation represents a new observation of precipitate formation and potential marine deposition in polar seas.

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FREZCHEM: A geochemical model for cold aqueous solutions

Cited by 85 publications

References 19 publications

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

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

Temporal dynamics of ikaite in experimental sea ice

Gypsum crystals observed in experimental and natural sea ice

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FREZCHEM: A geochemical model for cold aqueous solutions

Cited by 85 publications

References 19 publications

Ikaite crystal distribution in winter sea ice and implications for CO&lt;sub&gt;2&lt;/sub&gt; system dynamics

Ikaite crystal distribution in winter sea ice and implications for CO&lt;sub&gt;2&lt;/sub&gt; system dynamics

Temporal dynamics of ikaite in experimental sea ice

Gypsum crystals observed in experimental and natural sea ice

Contact Info

Product

Resources

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

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