 |
| Titel |
Temporal dynamics of ikaite in experimental sea ice |
| VerfasserIn |
S. Rysgaard, F. Wang, R. J. Galley, R. Grimm, D. Notz, M. Lemes, N.-X. Geilfus, A. Chaulk, A. A. Hare, O. Crabeck, B. G. T. Else, K. Campbell, L. L. Sørensen, J. Sievers, T. Papakyriakou |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1994-0416
|
| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 8, no. 4 ; Nr. 8, no. 4 (2014-08-08), S.1469-1478 |
| Datensatznummer |
250116261
|
| Publikation (Nr.) |
 copernicus.org/tc-8-1469-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Ikaite (CaCO3 · 6H2O) is a metastable phase of calcium
carbonate that normally forms in a cold environment and/or under high
pressure. Recently, ikaite crystals have been found in sea ice, and it has
been suggested that their precipitation may play an important role in
air–sea CO2 exchange in ice-covered seas. Little is known, however, of
the spatial and temporal dynamics of ikaite in sea ice. Here we present
evidence for highly dynamic ikaite precipitation and dissolution in sea ice
grown at an outdoor pool of the Sea-ice Environmental Research Facility
(SERF) in Manitoba, Canada. During the experiment, ikaite precipitated in
sea ice when temperatures were below −4 °C, creating three distinct
zones of ikaite concentrations: (1) a millimeter-to-centimeter-thin surface layer containing
frost flowers and brine skim with bulk ikaite concentrations of >2000 μmol kg−1,
(2) an internal layer with ikaite concentrations of 200–400 μmol kg−1, and (3) a bottom layer with
ikaite concentrations of <100 μmol kg−1. Snowfall
events caused the sea ice to warm and ikaite crystals to dissolve. Manual
removal of the snow cover allowed the sea ice to cool and brine salinities
to increase, resulting in rapid ikaite precipitation. The observed ikaite
concentrations were on the same order of magnitude as modeled by
FREZCHEM, which further supports the notion that ikaite concentration in sea ice
increases with decreasing temperature. Thus, varying snow conditions may
play a key role in ikaite precipitation and dissolution in sea ice. This
could have a major implication for CO2 exchange with the atmosphere and
ocean that has not been accounted for previously. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|