References of "Dieckmann, Gerhard"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailIncorporation of iron and organic matter into young Antarctic sea ice during its initial growth stages
Janssens, Julie; Meiners, Klaus M.; Tison, Jean-Louis et al

in Elementa: Science of the Anthropocene (2016), 4(1), 000123

This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for ... [more ▼]

This study reports concentrations of iron (Fe) and organic matter in young Antarctic pack ice and during its initial growth stages in situ. Although the importance of sea ice as an Fe reservoir for oceanic waters of the Southern Ocean has been clearly established, the processes leading to the enrichment of Fe in sea ice have yet to be investigated and quantified. We conducted two in situ sea-ice growth experiments during a winter cruise in the Weddell Sea. Our aim was to improve the understanding of the processes responsible for the accumulation of dissolved Fe (DFe) and particulate Fe (PFe) in sea ice, and of particulate organic carbon and nitrogen, dissolved organic carbon, extracellular polymeric substances, inorganic macro-nutrients (silicic acid, nitrate and nitrite, phosphate and ammonium), chlorophyll a and bacteria. Enrichment indices, calculated for natural young ice and ice newly formed in situ, indicate that during Antarctic winter all of the measured forms of particulate matter were enriched in sea ice compared to underlying seawater, and that enrichment started from the initial stages of sea-ice formation. Some dissolved material (DFe and ammonium) was also enriched in the ice but at lower enrichment indices than the particulate phase, suggesting that size is a key factor for the incorporation of impurities in sea ice. Low chlorophyll a concentrations and the fit of the macro-nutrients (with the exception of ammonium) with their theoretical dilution lines indicated low biological activity in the ice. From these and additional results we conclude that physical processes are the dominant mechanisms leading to the enrichment of DFe, PFe, organic matter and bacteria in young sea ice, and that PFe and DFe are decoupled during sea-ice formation. Our study thus provides unique quantitative insight into the initial incorporation of impurities, in particular DFe and PFe, into Antarctic sea ice. [less ▲]

Detailed reference viewed: 22 (1 ULg)
Full Text
See detailThe study of air-ice CO2 exchange emphasize the importance of gas bubble transport during sea ice growth
Kotovitch, Marie ULg; Moreau, Sébastien; Zhou, Jiayun et al

Poster (2015, August 20)

We report air-ice CO2 fluxes measured continuously using automated chambers over artificial sea ice from freezing to decay. We observed an uptake of CO2 as seawater was cooling down prior to sea ice ... [more ▼]

We report air-ice CO2 fluxes measured continuously using automated chambers over artificial sea ice from freezing to decay. We observed an uptake of CO2 as seawater was cooling down prior to sea ice formation. As soon as the first ice crystals started to form, we observed a shift from a sink to a source. Sea ice released CO2 until we initiated the ice decay by warming the atmosphere. Sea ice then returned to be a CO2 sink. Direct measurements of the fluxes were consistent with the depletion of dissolved inorganic carbon in sea ice. Measurements of bulk partial pressure of CO2 in sea ice and of atmospheric CO2 allowed us to assess a gas exchange coefficient for CO2 at the air-sea ice interface during the grow stage. We compared these observations with a 1D biogeochemical model. Discrepancies between the model and the observations lead us to emphasize the role of gas bubbles in CO2 transport through sea ice. [less ▲]

Detailed reference viewed: 64 (5 ULg)
See detailMeasurements of air-ice CO2 fluxes over artificial sea ice emphasize the role of bubbles in gas transport
Kotovitch, Marie ULg; Moreau, Sébastion; Zhou, Jiayun et al

Poster (2015, March)

Detailed reference viewed: 29 (3 ULg)
Full Text
Peer Reviewed
See detailSea ice contribution to the air-sea CO2 exchange in the Arctic and Southern Oceans
Rysgaard, Søren; Bendtsen; Delille, Bruno ULg et al

in Tellus : Series B (2011), 63(5), 823-830

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO2 and the subsequent effect on air–sea CO2 exchange have received little ... [more ▼]

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO2 and the subsequent effect on air–sea CO2 exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air–sea CO2 exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO2 uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO2 uptake in ice-free polar seas. This sea-ice driven CO2 uptake has not been considered so far in estimates of global oceanic CO2 uptake. Net CO2 uptake in sea-ice–covered oceans can be driven by; (1) rejection during sea–ice formation and sinking of CO2-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air–sea CO2 exchange during winter, and (3) release of CO2-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO2 drawdown during primary production in sea ice and surface oceanic waters. [less ▲]

Detailed reference viewed: 51 (0 ULg)
See detailpCO2 dynamics and related airice CO2 fluxes during sea-ice growth and decay in an ice-tank experiment
Delille, Bruno ULg; Thomas, D. N.; Dieckmann, Gerhard et al

Poster (2010, June)

Detailed reference viewed: 12 (0 ULg)