Berichte aus dem MARUM und dem Fachbereich Geowissenschaften der Universität Bremen
Description / Table of Contents:
Emissions of free gas from sediments in glacial troughs into the water column were detected at the shelf of South Georgia during R/V POLARSTERN Cruise ANT‐XXIX/4 in 2013. Preliminary but not systematically conducted surveys of flare mapping have shown that the emissions are exclusively related to the shelf trough systems and probably sourced from the post‐glacial sediments by biogenically produced methane. During M134 with R/V METEOR the distribution of gas emission sites at eight cross‐shelf troughs were mapped. 2,647 nautical miles were mapped around South Georgia by using PARASOUND and multi‐beam systems EM710 and EM122. More than 1,600 gas emission sites were detected by acoustic anomalies in the water column data. The emission sites and the zones of blanking within sediment echo‐sounder records correlate well and are predominantly concentrated to the inner fjord systems, where higher rates of organic material seems to become deposited and leads to the formation of methane. Because of the cold bottom water seepage in areas deeper than 370 m water depth methane hydrate occurs in sediments of Church Trough and Annenkov Trough. Based on the analysis of a Dynamic Autoclave Piston Corer and negative chloride concentrations in the pore water gas hydrate saturation up to 10% were quantified. Furthermore 10 dives with ROV MARUM SQUID were used to investigate methane emission sites at the seafloor. In total 21 gravity cores and 14 multicores have been taken to study biogeochemistry of sediments not only related to methane‐influenced diagenesis. Ikaite crystals of different shape and size have been found at various locations and probably seem to be widely distributed in these deposits around South Georgia. Diagenesis of iron was obvious in sediment cores by strong color changes and will be investigated more in detail. Water samples from 31 CTD/hydrocast stations, 12 bottom water sampler and 8 GoFlo stations have been taken for methane distribution and its fate in the water column. Water samples have also been taken in order to investigate iron transport to the ocean where iron as micro‐nutrient is used for phytoplankton productivity. The cruise started at Port Stanley of the Falkland Islands on 16 January and ended on 17 February in Punta Arenas Chile. In total a distance of 4,634 nautical miles were covered.
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Berichte aus dem MARUM und dem Fachbereich Geowissenschaften der Universtiät Bremen No. 317
Erscheint auch als R/V METEOR Cruise Report M134
Lower compact magazine