RV AEGAEO Fahrtbericht / Cruise Report, West Nile Delta Project Cruise - WND-V, 15.06. – 25.06.2010, Heraklion- Heraklion (Greece)

Cruise WND-V was the fifth and final expedition of the West Nile Delta project carried out at IFM-GEOMAR with support from RWE-Dea. On this concluding cruise of the project, the two mud volcanoes North Alex and Giza were once again visited, this time using the Greek R/V AEGAEO. The primary purpose of the WND-V cruise was the recovery of instruments and observatories which had been deployed in or near the active centers of North Alex and Giza MVs over the past 30 months. In addition, complementary new data were acquired that were needed to better quantify the methane flux from the centers of both MVs. From 15 to 25 June 2010, the following activities were carried out: · recovery of 12 long-term Ocean-Bottom-Seismometers (OBS) at North Alex MV, which had been deployed during POSEIDON cruise P388 in 2009. · recovery of 4 instruments for measuring long-term pore pressure variations (piezometers) on the slope near North Alex MV, deployed during POSEIDON cruise P388 in 2009. · recovery of 6 instruments for measuring long-term chemical flux (CATmeters) at Giza and North Alex MV. · recovery of 1 instrument (OBMets) for measuring methane flux from the seafloor at North Alex MV. · recovery of 2 tiltmeters for measuring seafloor deformation at North Alex MV. · recovery of 2 long-term temperature observatories at Giza and North Alex MV. · CTD casts in the central area of North Alex MV · Imaging of bubble streams from the active center of North Alex using an SIMRAD EK60 sonar system. Although hampered by poor weather during the final days of the cruise the recovery operations were finished two days earlier than expected. Bathymetric data acquisition however, which had been part of the original schedule had to be cancelled due to bad weather as well as technical problems with the deep water sonar systems.