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| Titel |
Ikaite crystal distribution in winter sea ice and implications for CO2 system dynamics |
| VerfasserIn |
S. Rysgaard, D. H. Søgaard, M. Cooper, M. Pućko, K. Lennert, T. N. Papakyriakou, F. Wang, N. X. Geilfus, R. N. Glud, J. Ehn, D. F. McGinnis, K. Attard, J. Sievers, J. W. Deming, D. Barber |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 7, no. 2 ; Nr. 7, no. 2 (2013-04-23), S.707-718 |
| Datensatznummer |
250017961
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| Publikation (Nr.) |
 copernicus.org/tc-7-707-2013.pdf |
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| Zusammenfassung |
| The precipitation of ikaite (CaCO3 ⋅ 6H2O) 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 × 106 crystals kg−1)
to values of 100–200 μmol kg−1 ice (1–7 × 106 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 pCO2 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 CO2. |
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