POS518: Week 4

19 – 26 October 2017

In the morning of 19 October, the BIGO Lander was deployed again and a gravity corer was taken for our colleagues at the NOC before the weather deteriorated. During 20 October, three CTD casts at the lander stations were performed. After this, an acoustic data link was established to verify that the NOC-Lander has started to record oceanographic and chemical data. Subsequently, the second BIGO deployment came to its end and the lander was retrieved successfully despite a significant swell providing a second valuable data set of benthic in situ fluxes. At this lander’s position a gravity corer was taken before RV POSEIDON set sail again for shelter in the Moray Firth. In the morning of 22 October, RV POSEIDON returned to the working area to retrieve the satellite lander and to perform a CTD cast during a large swell of the sea.

Sampling with the BIGO Lander (left) and recovery of the satellite lander (right). Images courtesy P.Linke

Subsampling of a gravity corer on deck (left). Geochemical analyses of water column and porewater samples in the dry lab (right). Images courtesy P.Linke.

Since the weather forecast was favourable for the night and early morning only, we headed for a position further to the east to obtain a CTD cast and a sediment core for our colleagues from WP3. The weather deteriorated rapidly to Bft. 7, but we were able to retrieve a 5.8m long sediment core at the flank of the Scanner Pockmark to sample sediments of the Witchground Formation. These sediments will be used to examine sub-seafloor structures and fluid pathways by sedimentological and geochemical measurements at GEOMAR.

Gravity corer sampling position at the Scanner Pockmark (image courtesy C. Böttner).

After securing all instrumentation on deck, station work was terminated due to increasing wind speeds and the unfavourable weather forecast. RV POSEIDON set sail for a southerly course around the storm for our return to Kiel Harbour. The transit provided the time to have a first look on the obtained data and write the preliminary cruise report. We will arrive on Friday morning to unload the vessel at the east shore campus of GEOMAR.

Despite the difficult weather conditions that caused a loss of 5 full working days, each scientist managed to get a useful data set to accomplish the project tasks of STEMM-CCS and prepare for the upcoming cruises in 2018 and 2019. This was possible only by the engaged and professional support of Captain Günther and his crew, which we would like to acknowledge at this point.

On behalf of all participants with best wishes,
Peter Linke, chief scientist

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