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| Titel |
Snow cover and short-term synoptic events drive biogeochemical dynamics in winter Weddell Sea pack ice (AWECS cruise - June to August 2013) |
| VerfasserIn |
Jean-louis Tison, Bruno Delille, Gerhard Dieckmann, Jeroen de Jong, Julie Janssens, Janne Rintala, Annemari Luhtanen, Niklaus Gussone, Christiane Uhlig, Daiki Nomura, Véronique Schoemann, Jiayun Zhou, Gauthier Carnat, François Fripiat |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250087550
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| Publikation (Nr.) |
 EGU/EGU2014-1605.pdf |
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| Zusammenfassung |
| This paper presents the preliminary results of an integrated multidisciplinary study of pack
ice biogeochemistry in the Weddell Sea during the winter 2013 (June-August). The sea ice
biogeochemistry group was one of the components of the AWECS (Antarctic Winter
Ecosystem and Climate Study) cruise (Polarstern ANTXXIX-6). A total of 12 stations were
carried out by the sea ice biogeochemistry group, which collected a suite of variables in the
fields of physics, inorganic chemistry, gas content and composition, microbiology,
biogeochemistry, trace metals and the carbonate system in order to give the best possible
description of the sea ice cover and its interactions at interfaces. Samples were collected in
the atmosphere above (gas fluxes), in the snow cover, in the bulk ice (ice cores), in the brines
(sackholes) and in the sea water below (0m, 1m, 30 m). Here we present the results of basic
physico-chemical (T°, bulk ice salinity, brine volumes, brine salinity, Rayleigh numbers) and
biological (Chla) measurements in order to give an overview of the general status of the
Weddell Sea winter pack ice encountered, and discuss how it controls climate relevant
biogeochemical processes. Our results from the first set of 9 stations, mainly sampled along
the Greenwich meridian and the easternmost part of the Weddell Sea definitively
refute the view of a biogeochemically “frozen” sea ice during the Winter. This has
already been demonstrated for the Spring and Summer, but we now see that sea
ice sustains considerable biological stocks and activities throughout the Winter,
despite the reduced amount of available PAR radiation. Accretion of the snow cover
appears to play an essential role in driving biogeochemical activity, through warming
from insulation, thus favouring brine transport, be it through potential convection,
surface brine migration (brine tubes) or flooding. This results in a “widening” of the
internal autumn layer (quite frequent in this rafting-dominated sea ice cover) and
increase of the chla burden with age. Results from the second set of 3 stations in the
western branch of the Weddell Sea gyre confirm that it comprises a mixture of older
fast/second year ice floes with younger first-year ice floes. The older ice had the highest
Chlaconcentrations of the entire cruise (>200 μgl-1), in an internal community enclosed
within desalinized impermeable upper and lower layers. The first-year ice differs from that
in the eastern Weddell Sea as it is dominated by columnar ice and (weak) algal
communities are only found on the bottom or near the surface (no internal maximum). |
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