Gypsum crystals observed in experimental and natural sea ice

Geilfus, Nicolas-Xavier; Galley, R. J.; Cooper, M.; Halden, Norman M.; Hare, A.A.; Wang, Fei; Søgaard, Dorte Haubjerg; Rysgaard, Søren

doi:10.1002/2013gl058479

Cited by 37 publications

(71 citation statements)

References 33 publications

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“…Sea ice is melted in the pool by circulating heated ethylene glycol through a closed-loop hose located at the bottom of the pool, allowing successive ice growth/melt experiments to be carried out during one winter. The experimental sea ice and brine exhibit similar physical and chemical properties to those observed in natural Arctic sea ice (Geilfus et al, 2013b;Hare et al, 2013). The experiment described herein was initiated from open water conditions on 11 January 2013 when the heater was turned off.…”

Section: Site Description Sampling and Analysismentioning

confidence: 88%

“…As a result, the concentration of dissolved salts, including inorganic carbon, increases within the brine and promotes the precipitation of calcium carbonate crystals such as ikaite (CaCO 3 q 6H 2 O) (Marion, 2001). These crystals have been reported in both natural (Dieckmann et al, 2008;Nomura et al, 2013;Søgaard et al, 2013) and experimental sea ice (Geilfus et al, 2013b;Rysgaard et al, 2014) and have been suggested to be a key component of the carbonate system Fransson et al, 2013;.…”

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confidence: 82%

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Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

et al. 2016

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Abstract. The precipitation of ikaite and its fate within sea ice is still poorly understood. We quantify temporal inorganic carbon dynamics in sea ice from initial formation to its melt in a sea ice-seawater mesocosm pool from 11 to 29 January 2013. Based on measurements of total alkalinity (TA) and total dissolved inorganic carbon (TCO 2 ), the main processes affecting inorganic carbon dynamics within sea ice were ikaite precipitation and CO 2 exchange with the atmosphere. In the underlying seawater, the dissolution of ikaite was the main process affecting inorganic carbon dynamics. Sea ice acted as an active layer, releasing CO 2 to the atmosphere during the growth phase, taking up CO 2 as it melted and exporting both ikaite and TCO 2 into the underlying seawater during the whole experiment. Ikaite precipitation of up to 167 µmol kg −1 within sea ice was estimated, while its export and dissolution into the underlying seawater was responsible for a TA increase of 64-66 µmol kg −1 in the water column. The export of TCO 2 from sea ice to the water column increased the underlying seawater TCO 2 by 43.5 µmol kg −1 , suggesting that almost all of the TCO 2 that left the sea ice was exported to the underlying seawater. The export of ikaite from the ice to the underlying seawater was associated with brine rejection during sea ice growth, increased vertical connectivity in sea ice due to the upward percolation of seawater and meltwater flushing during sea ice melt. Based on the change in TA in the water column around the onset of sea ice melt, more than half of the total ikaite precipitated in the ice during sea ice growth was still contained in the ice when the sea ice began to melt. Ikaite crystal dissolution in the water column kept the seawater pCO 2 undersaturated with respect to the atmosphere in spite of increased salinity, TA and TCO 2 associated with sea ice growth. Results indicate that ikaite export from sea ice and its dissolution in the underlying seawater can potentially hamper the effect of oceanic acidification on the aragonite saturation state ( aragonite ) in fall and in winter in ice-covered areas, at the time when aragonite is smallest.

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Section: Site Description Sampling and Analysismentioning

confidence: 88%

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confidence: 82%

Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

et al. 2016

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“…Actually, CaSO 4 is well known as a major mineral constituent (gypsum). Moreover, Marion and Farren (1999) and Geilfus et al (2013) pointed out CaSO 4 (gypsum) formation by seasalt fractionation on sea ice in polar regions. However, the origins of CaSO 4 particles in the Antarctic atmosphere remain unclear.…”

Section: Aerosol Constituents and Mixing States During The Jase Traversementioning

confidence: 99%

Horizontal distributions of aerosol constituents and their mixing states in Antarctica during the JASE traverse

et al. 2014

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Abstract. Measurements of aerosol number concentrations and direct aerosol sampling were conducted on continental Antarctica during the traverse of the Japanese-Swedish joint Antarctic expedition (JASE) from 14 November 2007 until 24 January 2008. Aerosol concentrations in background conditions decreased gradually with latitude in inland regions during the traverse. The lowest aerosol number concentrations were 160 L −1 in D p > 0.3 µm, and 0.5 L −1 in D p > 2 µm. In contrast, aerosol concentrations reached 3278 L −1 in D p > 0.3 µm, and 215 L −1 in D p > 2 µm under strong wind conditions. The estimated aerosol mass concentrations were 0.04-5.7 µg m −3 . Single particle analysis of aerosol particles collected during the JASE traverse was conducted using a scanning electron microscope equipped with an energy dispersive x ray spectrometer. Major aerosol constituents were sulfates in fine mode, and sulfate, sea salts, modified sea salts, and fractionated sea salts in coarse mode. K-rich sulfates, Mg-rich sulfate, Ca-rich sulfates, and minerals were identified as minor aerosol constituents. Horizontal features of Cl / Na ratios imply that sea-salt modification (i.e. Cl loss) occurred on the Antarctic continent during the summer. Most sea-salt particles in the continental region near the coast were modified with acidic sulfur species such as H 2 SO 4 and CH 3 SO 3 H. By contrast, acidic species other than the acidic sulfur species (likely HNO 3 ) contributed markedly to sea-salt modification in inland areas during the traverse. Mg-rich sea-salt particles and Mg-free sea-salt particles were present in coarse and fine modes from the coast to inland areas. These sea-salt particles might be associated with sea-salt fractionation on the snow surface of continental Antarctica.

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“…Hence, sea ice acts as a carbon pump during spring and summer. In contrast, during ice formation there are indications that sea ice acts as a CO 2 source as a consequence of the concentration of solutes in brines, CaCO 3 precipitation and microbial respiration (Geilfus et al, 2013b;Nomura et al, 2006;Tison et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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Abstract. We present the CH 4 concentration [CH 4 ], the partial pressure of CO 2 (pCO 2 ) and the total gas content in bulk sea ice from subarctic, land-fast sea ice in the Kapisillit fjord, Greenland. Fjord systems are characterized by freshwater runoff and riverine input and based on δ 18 O data, we show that > 30 % of the surface water originated from periodic river input during ice growth. This resulted in fresher sea-ice layers with higher gas content than is typical from marine sea ice. The bulk ice [CH 4 ] ranged from 1.8 to 12.1 nmol L −1 , which corresponds to a partial pressure ranging from 3 to 28 ppmv. This is markedly higher than the average atmospheric methane content of 1.9 ppmv. Evidently most of the trapped methane within the ice was contained inside bubbles, and only a minor portion was dissolved in the brines. The bulk ice pCO 2 ranged from 60 to 330 ppmv indicating that sea ice at temperatures above −4 • C is undersaturated compared to the atmosphere (390 ppmv). This study adds to the few existing studies of CH 4 and CO 2 in sea ice, and we conclude that subarctic seawater can be a sink for atmospheric CO 2 , while being a net source of CH 4 .

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Gypsum crystals observed in experimental and natural sea ice

Cited by 37 publications

References 33 publications

Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

Horizontal distributions of aerosol constituents and their mixing states in Antarctica during the JASE traverse

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

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Gypsum crystals observed in experimental and natural sea ice

Cited by 37 publications

References 33 publications

Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

Estimates of ikaite export from sea ice to the underlying seawater in a sea ice–seawater mesocosm

Horizontal distributions of aerosol constituents and their mixing states in Antarctica during the JASE traverse

CO&lt;sub&gt;2&lt;/sub&gt; and CH&lt;sub&gt;4&lt;/sub&gt; in sea ice from a subarctic fjord under influence of riverine input

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