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| Titel |
Sea-ice melt CO2–carbonate chemistry in the western Arctic Ocean: meltwater contributions to air–sea CO2 gas exchange, mixed-layer properties and rates of net community production under sea ice |
| VerfasserIn |
N. R. Bates, R. Garley, K. E. Frey, K. L. Shake, J. T. Mathis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 23 ; Nr. 11, no. 23 (2014-12-08), S.6769-6789 |
| Datensatznummer |
250117716
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| Publikation (Nr.) |
 copernicus.org/bg-11-6769-2014.pdf |
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| Zusammenfassung |
| The carbon dioxide (CO2)-carbonate chemistry of sea-ice melt and
co-located, contemporaneous seawater has rarely been studied in sea-ice-covered oceans. Here, we describe the CO2–carbonate chemistry of sea-ice
melt (both above sea-ice as "melt ponds" and below sea-ice as "interface
waters") and mixed-layer properties in the western Arctic Ocean in the early
summer of 2010 and 2011. At 19 stations, the salinity (∼0.5 to
<6.5), dissolved inorganic carbon (DIC; ∼20 to
<550 μmol kg−1) and total alkalinity (TA; ∼30 to
<500 μmol kg−1) of above-ice melt pond water was low
compared to the co-located underlying mixed layer. The partial pressure of
CO2 (pCO2) in these melt ponds was highly variable
(∼<10 to >1500 μatm) with the majority of melt ponds
acting as potentially strong sources of CO2 to the atmosphere. The pH of
melt pond waters was also highly variable ranging from mildly acidic (6.1 to
7) to slightly more alkaline than underlying seawater (>8.2 to 10.8). All
of the observed melt ponds had very low (<0.1) saturation states (Ω) for calcium carbonate (CaCO3) minerals such as aragonite (Ωaragonite). Our data suggest that sea-ice generated alkaline or
acidic type melt pond water. This melt water chemistry dictates whether the
ponds are sources of CO2 to the atmosphere or CO2 sinks. Below-ice
interface water CO2–carbonate chemistry data also indicated substantial
generation of alkalinity, presumably owing to dissolution of CaCO3 in
sea-ice. The interface waters generally had lower pCO2 and higher
pH/Ωaragonite than the co-located mixed layer beneath.
Sea-ice melt thus contributed to the suppression of mixed-layer pCO2,
thereby enhancing the surface ocean's capacity to uptake CO2 from the
atmosphere. Our observations contribute to growing evidence that sea-ice
CO2–carbonate chemistry is highly variable and its contribution to the
complex factors that influence the balance of CO2 sinks and sources (and
thereby ocean acidification) is difficult to predict in an era of rapid
warming and sea-ice loss in the Arctic Ocean. |
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