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Author |
Mock, T.; Dieckmann, G.S.; Haas, C.; Krell, A.; Tison, J.-L.; Belem, A.L.; Papadimitriou, S.; Thomas, D.N. |
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Title |
Micro-optodes in sea ice: a new approach to investigate oxygen dynamics during sea ice formation |
Type |
Journal Article |
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Year |
2002 |
Publication |
Aquatic Microbial Ecology |
Abbreviated Journal |
Aquat Microb Ecol |
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Volume |
29 |
Issue |
3 |
Pages |
297-306 |
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Keywords |
Fragilariopsis cylindrus; Oxygen; Methods; Micro-optodes; Sea ice; Biogeochemistry; Diatoms; Algae; Chlorophyll; Photosynthesis; Salinity effects; Sea water; Marine ecosystems; Chlorophylls; Dissolved oxygen; Gases; Epontic environment; Electrodes; Sensors; Brines; Ice-water interface; Ice formation; Bacillariophyceae |
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Abstract |
Oxygen micro-optodes were used to measure oxygen dynamics directly within the microstructure of sea ice by freezing the sensors into the ice during its formation. The experiment was conducted in a 4 m³ mesocosm filled with artificial seawater and inoculated with a unialgal culture of the common Antarctic ice diatom Fragilariopsis cylindrus (Bacillariophyceae) to a final chlorophyll a (chl a) concentration of 11 µg 1?¹. Ice growth was initiated 7 d after inoculation by reducing the air temperature to -10 plus or minus 2 degree C and terminated 17 d later. The final ice thickness was 27 cm. One optode was frozen into grease ice and 2 others into the skeletal layer of the growing ice sheet. Increasing oxygen concentrations during ice crystal formation at the water surface and the ice-water interface revealed a strong inclusion of oxygen, which was either physically trapped and/or the result of photosynthesising diatoms. The major portion of oxygen was present as gas bubbles due to super-saturation as a result of increasing salinity and oxygen production by diatoms. An increase in salinity due to a concurrent decrease in ice temperatures during subsequent sea ice development reduced the maximum concentration of dissolved oxygen within brine. Thus, dissolved oxygen concentrations decreased over time, whereas gaseous oxygen was released to the atmosphere and seawater. The sensors are a significant advance on more conventional microelectrodes, because the recordings can be temperature and salinity compensated in order to obtain precise measurements of oxygen dynamics with regard to total (dissolved and gaseous) and dissolved oxygen in sea ice. Optodes do not consume oxygen during measuremnet over a long period under extreme conditions, which is another advantage for long-term deployment in the field. |
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Inter-Research |
Place of Publication |
Oldendorf/Luhe |
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ISSN |
0948-3055 |
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Notes |
Marine |
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no |
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Call Number |
refbase @ admin @ Mock++2002 |
Serial |
749 |
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Author |
Giannelli, V.; Thomas, D.N.; Haas, C.; Kattner, G.; Kennedy, H.; Dieckmann, G.S. |
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Title |
Behaviour of dissolved organic matter and inorganic nutrients during experimental sea-ice formation |
Type |
Journal Article |
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Year |
2001 |
Publication |
Annals of Glaciology |
Abbreviated Journal |
Ann Glaciol |
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Volume |
33 |
Issue |
1 |
Pages |
317-321 |
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Abstract |
It is well established that during sea-ice formation, crystals aggregate into a solid matrix, and dissolved sea-water constituents, including inorganic nutrients, are rejected from the ice matrix. However, the behaviour of dissolved organic matter (DOM) during ice formation and growth has not been studied to date. DOM is the primary energetic substrate for microbial heterotrophic activity in sea water and sea ice, and therefore it is at the base of the trophic fluxes within the microbial food web. The aim of our study was to compare the behaviour of DOM and inorganic nutrients during formation and growth of sea ice. Experiments were conducted in a large indoor ice-tank facility (Hamburg Ship Model Basin, Germany) at -15°C. Three 1 m³ tanks, to which synthetic sea water, nutrients and dissolved organic compounds (diatom-extracted DOM) had been added, were sampled over a period of 5 days during sea-ice formation. Samples were collected throughout the experiment from water underlying the ice, and at the end from the ice as well. Brine was obtained from the ice by centrifuging ice cores. Inorganic nutrients (nitrate and phosphate) were substantially enriched in brine in comparison to water and ice phases, consistent with the processes of ice formation and brine rejection. Dissolved organic carbon (DOC) was also enriched in brine but was more variable and enriched in comparison to a dilution line. No difference in bacteria numbers was observed between water, ice and brine. No bacteria growth was measured, and this therefore had no influence on the measurable DOC levels. We conclude that the incorporation of dissolved organic compounds in newly forming ice is conservative. However, since the proportions of DOC in the brine were partially higher than those of the inorganic nutrients, concentrating effects of DOC in brine might be different compared to salts. |
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International Glaciological Society |
Place of Publication |
Cambridge |
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Intl. Symp. on Sea Ice and its Interaction with the Ocean, A. and B., Fairbanks, Alaska(USA), 19-23 Jun 2000, |
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ISSN |
0260-3055 |
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no |
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Call Number |
refbase @ admin @ Giannelli++2001 |
Serial |
732 |
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Author |
Granskog, M.A.; Virkkunen, K.; Thomas, D.N.; Ehn, J.; Kola, H.; Martma, T. |
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Title |
Chemical properties of brackish water ice in the Bothnian Bay, the Baltic Sea |
Type |
Journal Article |
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Year |
2004 |
Publication |
Journal of Glaciology |
Abbreviated Journal |
J Glaciol |
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Volume |
50 |
Issue |
169 |
Pages |
292-302 |
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Keywords |
Dependent Solute Redistribution; Dissolved Organic Matter; Phase Boundary; Sulfate; Binding; Summer; Oxygen; Core; Gulf |
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Abstract |
The behavior of majors, δ18O, dissolved organic carbon (DOC) and trace elements was studied during the initial freezing of low-saline water (3 practical salinity units) in a freezing experiment. Samples were also collected from first-year sea ice from pack ice in the Bothnian Bay, northern Baltic Sea. During initial ice formation, the major-ion ratios in sea ice indicated variable behavior, with some ions showing relative enrichment (sulfate, calcium and magnesium), conservative behavior (sodium) or relative depletion (potassium) compared to sea water at the same salinity DOC, iron and aluminum showed enrichment in the ice, while zinc was depleted to salinity. Lead was detected in surface snow-ice layers only, implying atmospheric accumulation. First-year sea ice, with a variable growth and thermal history, showed behavior for major ions similar to that observed in new ice. However, for trace elements the picture was much more complicated, most likely due to active secondary processes such as atmospheric supply and biological activity. Ice growth has a potential impact on the chemical budgets and cycling of some elements, especially those which are selectively rejected/retained during sea-ice formation, particularly in the shallow parts of the Bothnian Bay covered with a land-fast ice cover. |
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Address |
Granskog: Univ Helsinki, Dept Phys Sci, Div Geophys, FIN-00014 Helsinki, Finland |
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International Glaciological Society |
Place of Publication |
Cambridge |
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ISSN |
0022-1430 |
ISBN |
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Baltic Sea; Bothnian Bay |
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Notes |
ISI:000227720900014 |
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no |
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Call Number |
refbase @ admin @ Granskog++2004 |
Serial |
741 |
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Author |
Haas, C.; Thomas, D.N.; Bareiss, J. |
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Title |
Surface properties and processes of perennial Antarctic sea ice in summer |
Type |
Journal Article |
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Year |
2001 |
Publication |
Journal of Glaciology |
Abbreviated Journal |
J Glaciol |
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Volume |
47 |
Issue |
159 |
Pages |
613-625 |
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Abstract |
Ice-core and snow data from the Amundsen, Bellingshausen and Weddell Seas, Antarctica, show that the formation of superimposed ice and the development of seawater-filled gap layers with high algal standing stocks is typical of the perennial sea ice in summer. The coarse-grained and dense snow had salinities mostly below 0.1ppt. A layer of fresh superimposed ice had a mean thickness of 0.04-0.12 m. Gap layers 0.04-0.08 m thick extended downwards from 0.02 to 0.14 m below the water level. These gaps were populated by diatom standing stocks up to 439 ?g L?¹ chlorophyll a. We propose a comprehensive heuristic model of summer processes, where warming and the reversal of temperature gradients cause major transformations in snow and ice properties. The warming also causes the reopening of incompletely frozen slush layers caused by flood-freeze cycles during winter. Alternatively, superimposed ice forms at the cold interface between snow and slush in the case of flooding with negative freeboard. Combined, these explain the initial formation of gap layers by abiotic means alone. The upward growth of superimposed ice above the water level competes with a steady submergence of floes due to bottom and internal melting and accumulation of snow. |
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Publisher |
International Glaciological Society |
Place of Publication |
Cambridge |
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Summary Language |
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Abbreviated Series Title |
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0022-1430 |
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Notes |
IPØ/Tvärrminne |
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no |
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Call Number |
refbase @ admin @ Haas++2001 |
Serial |
742 |
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Author |
Steffens, M.; Granskog, M.A.; Kaartokallio, H.; Kuosa, H.; Luodekari, K.; Papadimitriou, S.; Thomas, D.N. |
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Title |
Spatial variation of biogeochemical properties of landfast sea ice in the Gulf of Bothnia, Baltic Sea |
Type |
Conference Article |
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Year |
2006 |
Publication |
Annals of Glaciology |
Abbreviated Journal |
Ann Glaciol |
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Volume |
44 |
Issue |
1 |
Pages |
80-87 |
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Keywords |
Sea ice; Fast ice; Sea ice properties; Ice algae; Chlorophyll; Biogeochemistry; Nutrients (mineral); Particulate organic matter; Dissolved organic matter; Salinity; Spatial scale; Spatial variability; Horizontal patchiness; Sampling design; Brackish water; Ane; Baltic Sea; Gulf of Bothnia |
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Abstract |
Horizontal variation of landfast sea-ice properties was studied in the Gulf of Bothnia, Baltic Sea, during March 2004. In order to estimate their variability among and within different spatial levels, 72 ice cores were sampled on five spatial scales (with spacings of 10 cm, 2.5 m, 25 m, 250 m and 2.5 km) using a hierarchical sampling design. Entire cores were melted, and bulk-ice salinity, concentrations of chlorophyll a (Chl a), phaeophytin (Phaeo), dissolved nitrate plus nitrite (DIN) as well as dissolved organic carbon (DOC) and nitrogen (DON) were determined. All sampling sites were covered by a 5.5-23 cm thick layer of snow. Ice thicknesses of cores varied from 26 to 58 cm, with bulk-ice salinities ranging between 0.2 and 0.7 as is typical for Baltic Sea ice. Observed values for Chl a (range: 0.8-6.0 μg Chl a l-1; median: 2.9 μg Chl a l -1) and DOC (range: 37-397 μM; median: 95 μM) were comparable to values reported by previous sea-ice studies from the Baltic Sea. Analysis of variance among different spatial levels revealed significant differences on the 2.5 km scale for ice thickness, DOC and Phaeo (with the latter two being positively correlated with ice thickness). For salinity and Chl a, the 250 m scale was found to be the largest scale where significant differences could be detected, while snow depth only varied significantly on the 25 m scale. Variability on the 2.5 m scale contributed significantly to the total variation for ice thickness, salinity, Chl a and DIN. In the case of DON, none of the investigated levels exhibited variation that was significantly different from the considerable amount of variation found between replicate cores. Results from a principal component analysis suggest that ice thickness is one of the main elements structuring the investigated ice habitat on a large scale, while snow depth, nutrients and salinity seem to be of secondary importance. |
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Thesis |
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Publisher |
International Glaciological Society |
Place of Publication |
Cambridge |
Editor |
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Language |
English |
Summary Language |
English |
Original Title |
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ISSN |
0260-3055 |
ISBN |
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Area |
Baltic Sea; Gulf of Bothnia |
Expedition |
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Conference |
International Symposium on Sea Ice, Dunedin (New Zealand), 5-9 Dec 2005 |
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Notes |
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Approved |
no |
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Call Number |
refbase @ admin @ Steffens++2006 |
Serial |
754 |
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