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

Abstract

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 .

Sea ice <i>p</i>CO<sub>2</sub> dynamics and air–ice CO<sub>2</sub> fluxes during the Sea Ice Mass Balance in the Antarctic (SIMBA) experiment – Bellingshausen Sea, Antarctica

“…This uptake was on the same order of magnitude as previous fluxes reported over Antarctic sea ice during the austral summer by Delille (2006) and Nomura et al (2013) and over Arctic sea ice by Semiletov et al (2004), Nomura et al (2010a, b), and Geilfus et al (2012aGeilfus et al ( , 2013, using similar chamber techniques. At the Brussels site, fluxes measured over snow were similar to those measured over bare ice, suggesting the thin snow cover had a limited impact on CO 2 exchange between the atmosphere and sea ice.…”

“…The relationships between bulk ice pCO 2 (in µatm) and temperature measured in Antarctic (this study) and Arctic (Geilfus et al, 2012bCrabeck et al, 2014) sea ice; (b) zoom-in on the data from (a); (c) the relationships between in situ brine pCO 2 (in µatm) and brine temperature in the Antarctic (this study; Delille, 2006;Delille et al, 2007) and Arctic sea ice (Geilfus et al, 2012a); (d) relationship between the bulk ice pCO 2 (in µatm) and the brine volume fraction (in %) measured in Antarctic (this study) and Arctic (Geilfus et al, 2012bCrabeck et al, 2014) sea ice. Nomura et al (2010b), a snow cover thicker than 9 cm did not seem to completely prevent the CO 2 exchanges between the ice and the atmosphere.…”

“…10b and c, one-way ANOVA; F 1,210 = 30.73, p < 0.001); however, differences in the sea ice texture and dynamical forcing between the two poles are important and may have substantial effects on permeability (and therefore fluxes) and should be further investigated. It is noteworthy that the observed range of concentrations suggests that Antarctic sea ice becomes undersaturated in CO 2 relative to the atmosphere early in the winter-spring transition and reaches levels not observed in Arctic sea ice until much later in the spring decay process (Geilfus et al, 2012aCrabeck et al, 2014).…”

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

“…The ice characteristics in the Barrow study were similar to this Resolute Passage survey: a nearly isothermal ice cover (approaching 0 • C), low salinity in the sea ice surface layer (0-20 cm) and melt ponds at the surface of the ice (Zhou et al, 2013). Crabeck et al (2014) also reported sea ice pCO 2 [bulk] from SW Greenland. However, the concentrations reported in this work are on the lower end compared with the concentrations of 77-330 µatm reported by Crabeck et al (2014) due in part to warmer sea ice leading to a lower pCO 2 due to brine dilution by fresh meltwater (Fig.…”

“…Crabeck et al (2014) also reported sea ice pCO 2 [bulk] from SW Greenland. However, the concentrations reported in this work are on the lower end compared with the concentrations of 77-330 µatm reported by Crabeck et al (2014) due in part to warmer sea ice leading to a lower pCO 2 due to brine dilution by fresh meltwater (Fig. 5) and/or dissolution of ikaite.…”