On the relation between organic and inorganic carbon in the Weddell Sea
In: Journal of Marine Systems. Elsevier: Tokyo; Oxford; New York; Amsterdam. ISSN 0924-7963; e-ISSN 1879-1573, more
Also appears in:Le Fèvre, J.; Tréguer, P. (Ed.) (1998). Carbon Fluxes and Dynamic Processes in the Southern Ocean: Present and Past. Selected papers from the International JGOFS Symposium, Brest, France, 28-31 August 1995. Journal of Marine Systems, 17(1-4). Elsevier: Amsterdam. 1-619 pp., more
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| Keywords |
Cycles > Chemical cycles > Geochemical cycle > Biogeochemical cycle > Nutrient cycles > Carbon cycle
Humic substances
Inorganic matter > Carbon > Inorganic carbon
Organic matter > Carbon > Organic carbon
PSW, Antarctica [Marine Regions]; PSW, Weddell Sea [Marine Regions]
Marine/Coastal |
| Authors | | Top |
- Wedborg, M.
- Hoppema, M.
- Skoog, A.
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| Abstract |
Carbon cycling in the Weddell Sea was investigated during the ANT X/7 cruise with `FS Polarstern' December 1992–January 1993. Samples were taken on a cross section from Kapp Norvegia to Joinville Island, and on a section from the Larsen Ice Shelf to the northeast. The following quantities were measured: total carbon dioxide (TCO2), fluorescence from humic substances and total organic carbon. The distribution of TCO2 was strongly positively correlated to the time elapsed since the various water masses were last ventilated. In general, humic substance fluorescence was positively correlated with TCO2, with the exception of the productive part of the western Weddell Sea, where the correlation was negative in the surface mixed layer. The increased fluorescence at the surface is suggested to be a result of biological production. The distribution of total organic carbon showed less structure, since this quantity includes a particulate component, which is subject to dispersion processes different from those of the dissolved components TCO2 and humic substances. The mean total organic carbon concentration below the surface mixed layer was 50 μmol l−1. At some stations, a steep TOC maximum around 2000 m depth was observed. This was interpreted to result from mass sinking of phytoplankton blooms. Total organic carbon had a maximum in surface water, and at some stations also a second subsurface maximum. In the Warm Deep Water (WDW), TCO2 and fluorescence had their maximum values, while total organic carbon tended to be low. In low productivity surface water in the eastern part of the Kapp Norvegia–Joinville Island section, the lowest flourescence was found. Surface water is eventually formed from Warm Deep Water, which had the highest fluorescence values, and therefore it is concluded that humic substances were removed in situ from surface water. In the central area of the Weddell Sea, TCO2 and fluorescence showed the highest Warm Deep Water maxima, while total organic carbon was low. The Warm Deep Water in this area is part of the so-called Central Intermediate Water which circulates for a long time within the Weddell Gyre. Reduced total organic carbon, which coincides with the most pronounced Central Intermediate Water characteristics, and high TCO2 can thus both be accounted for by continued degradation of organic matter in this water mass. The associated fluorescence maximum implies that humic substances are also produced during mineralisation. Recently formed bottom water, by contrast, could be seen as patches of low TCO2, low fluorescence and high total organic carbon along the western slope of the Weddell Sea. |
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