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

Melt pond formation is a common feature of spring and summer Arctic sea ice, but the role and impact of sea ice melt and pond formation on both the direction and size of CO<sub>2</sub> fluxes between air and sea is still unknown. Here we report on the CO<sub>2</sub>–carbonate...

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Tác giả chính:	N.-X., Geilfus, R. J., Galley, O., Crabeck
Ngôn ngữ:	English
Năm xuất bản:	Copernicus Publications 2018
Chủ đề:	Science BiologyEcology Biology Geology
Truy cập Trực tuyến:	http://lrc.quangbinhuni.edu.vn:8181/dspace/handle/DHQB_123456789/3974
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spelling	oai:localhost:DHQB_123456789-39742018-10-22T08:44:07Z Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic N.-X., Geilfus R. J., Galley O., Crabeck Science BiologyEcology Science Biology Geology Melt pond formation is a common feature of spring and summer Arctic sea ice, but the role and impact of sea ice melt and pond formation on both the direction and size of CO<sub>2</sub> fluxes between air and sea is still unknown. Here we report on the CO<sub>2</sub>–carbonate chemistry of melting sea ice, melt ponds and the underlying seawater as well as CO<sub>2</sub> fluxes at the surface of first-year landfast sea ice in the Resolute Passage, Nunavut, in June 2012. <br><br> Early in the melt season, the increase in ice temperature and the subsequent decrease in bulk ice salinity promote a strong decrease of the total alkalinity (TA), total dissolved inorganic carbon (<i>T</i>CO<sub>2</sub>) and partial pressure of CO<sub>2</sub> (<i>p</i>CO<sub>2</sub>) within the bulk sea ice and the brine. As sea ice melt progresses, melt ponds form, mainly from melted snow, leading to a low in situ melt pond <i>p</i>CO<sub>2</sub> (36 μatm). The percolation of this low salinity and low <i>p</i>CO<sub>2</sub> meltwater into the sea ice matrix decreased the brine salinity, TA and <i>T</i>CO<sub>2</sub>, and lowered the in situ brine <i>p</i>CO<sub>2</sub> (to 20 μatm). This initial low in situ <i>p</i>CO<sub>2</sub> observed in brine and melt ponds results in air–ice CO<sub>2</sub> fluxes ranging between −0.04 and −5.4 mmol m<sup>−2</sup> day<sup>−1</sup> (negative sign for fluxes from the atmosphere into the ocean). As melt ponds strive to reach <i>p</i>CO<sub>2</sub> equilibrium with the atmosphere, their in situ <i>p</i>CO<sub>2</sub> increases (up to 380 μatm) with time and the percolation of this relatively high concentration <i>p</i>CO<sub>2</sub> meltwater increases the in situ brine <i>p</i>CO<sub>2</sub> within the sea ice matrix as the melt season progresses. As the melt pond <i>p</i>CO<sub>2</sub> increases, the uptake of atmospheric CO<sub>2</sub> becomes less significant. However, since melt ponds are continuously supplied by meltwater, their in situ <i>p</i>CO<sub>2</sub> remains undersaturated with respect to the atmosphere, promoting a continuous but moderate uptake of CO<sub>2</sub> (~ −1 mmol m<sup>−2</sup> day<sup>−1</sup>) into the ocean. Considering the Arctic seasonal sea ice extent during the melt period (90 days), we estimate an uptake of atmospheric CO<sub>2</sub> of −10.4 Tg of C yr<sup>−1</sup>. This represents an additional uptake of CO<sub>2</sub> associated with Arctic sea ice that needs to be further explored and considered in the estimation of the Arctic Ocean's overall CO<sub>2</sub> budget. 2018-09-05T08:04:43Z 2018-09-05T08:04:43Z 2015 http://lrc.quangbinhuni.edu.vn:8181/dspace/handle/DHQB_123456789/3974 en Copernicus Publications
institution	Trung tâm Học liệu Đại học Quảng Bình (Dspace)
collection	Trung tâm Học liệu Đại học Quảng Bình (Dspace)
language	English
topic	Science BiologyEcology Science Biology Geology
spellingShingle	Science BiologyEcology Science Biology Geology N.-X., Geilfus R. J., Galley O., Crabeck Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic
description	Melt pond formation is a common feature of spring and summer Arctic sea ice, but the role and impact of sea ice melt and pond formation on both the direction and size of CO<sub>2</sub> fluxes between air and sea is still unknown. Here we report on the CO<sub>2</sub>–carbonate chemistry of melting sea ice, melt ponds and the underlying seawater as well as CO<sub>2</sub> fluxes at the surface of first-year landfast sea ice in the Resolute Passage, Nunavut, in June 2012. <br><br> Early in the melt season, the increase in ice temperature and the subsequent decrease in bulk ice salinity promote a strong decrease of the total alkalinity (TA), total dissolved inorganic carbon (<i>T</i>CO<sub>2</sub>) and partial pressure of CO<sub>2</sub> (<i>p</i>CO<sub>2</sub>) within the bulk sea ice and the brine. As sea ice melt progresses, melt ponds form, mainly from melted snow, leading to a low in situ melt pond <i>p</i>CO<sub>2</sub> (36 μatm). The percolation of this low salinity and low <i>p</i>CO<sub>2</sub> meltwater into the sea ice matrix decreased the brine salinity, TA and <i>T</i>CO<sub>2</sub>, and lowered the in situ brine <i>p</i>CO<sub>2</sub> (to 20 μatm). This initial low in situ <i>p</i>CO<sub>2</sub> observed in brine and melt ponds results in air–ice CO<sub>2</sub> fluxes ranging between −0.04 and −5.4 mmol m<sup>−2</sup> day<sup>−1</sup> (negative sign for fluxes from the atmosphere into the ocean). As melt ponds strive to reach <i>p</i>CO<sub>2</sub> equilibrium with the atmosphere, their in situ <i>p</i>CO<sub>2</sub> increases (up to 380 μatm) with time and the percolation of this relatively high concentration <i>p</i>CO<sub>2</sub> meltwater increases the in situ brine <i>p</i>CO<sub>2</sub> within the sea ice matrix as the melt season progresses. As the melt pond <i>p</i>CO<sub>2</sub> increases, the uptake of atmospheric CO<sub>2</sub> becomes less significant. However, since melt ponds are continuously supplied by meltwater, their in situ <i>p</i>CO<sub>2</sub> remains undersaturated with respect to the atmosphere, promoting a continuous but moderate uptake of CO<sub>2</sub> (~ −1 mmol m<sup>−2</sup> day<sup>−1</sup>) into the ocean. Considering the Arctic seasonal sea ice extent during the melt period (90 days), we estimate an uptake of atmospheric CO<sub>2</sub> of −10.4 Tg of C yr<sup>−1</sup>. This represents an additional uptake of CO<sub>2</sub> associated with Arctic sea ice that needs to be further explored and considered in the estimation of the Arctic Ocean's overall CO<sub>2</sub> budget.
author	N.-X., Geilfus R. J., Galley O., Crabeck
author_facet	N.-X., Geilfus R. J., Galley O., Crabeck
author_sort	N.-X., Geilfus
title	Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic
title_short	Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic
title_full	Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic
title_fullStr	Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic
title_full_unstemmed	Inorganic carbon dynamics of melt-pond-covered first-year sea ice in the Canadian Arctic
title_sort	inorganic carbon dynamics of melt-pond-covered first-year sea ice in the canadian arctic
publisher	Copernicus Publications
publishDate	2018
url	http://lrc.quangbinhuni.edu.vn:8181/dspace/handle/DHQB_123456789/3974
_version_	1717292462438875136
score	9,463379

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

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