Physical oceanography measurements at the Håkon Mosby mud volcano (LOOME)

The deployment of LOOME was performed by lowering the LOOME frame by winch, followed by positioning of the surface sensors across the most active site by ROV. The frame was placed on an inactive slab of hydrates, eastwards and adjacent to the hot spot. As part of the LOOME-frame Sun & Sea multi parameter probe CTD 60M was deployed approximately 3 m above the seafloor. The device was rated to 2000 m water depth. As energy supply a DeepSea Power & Light SeaBattery (12V) was used, which allows a run time of the CTD 60M of more than a year. The memory capacity of the probe is sufficient to allow data storage for more than a year as well, applying a time resolution of better than one measurement per minute. The probe was configured to start running when the energy supply is connected and a magnetic switch is closed. An LED on top of CTD is indicating the current state of the probe. The major aim was to record the temperature and pressure regime in the bottom water at the Håkon Mosby Mud Volcano.

Chemical sensor measurements at the sediment surface of the Håkon Mosby mud volcano (LOOME)

Six sensor units each having a pH, dissolved oxygen (DO) and oxidation reduction potential (ORP) sensor, plus a central logger, and connection cables were purchased from RBR (Ottawa). The sensing loggers were placed at a transect across the hot spot. Unfortunately, 5 of the 7 loggers were drowned. Only the central logger, that collected the data from the 6 sensor loggers, and one of the sensor loggers remained dry and functional. The sensor was positioned at 50 m south of the frame, in the center of the hot spot. The ORP did not show interpretable signals. The DO and pH signals showed good correlation (. At the end of October 2009 both signals decreased, the pH became as low as 4, possibly indicating increased seepage, or burial in expelled sediments. In December both sensors regained seawater values and then decreased again until the end of May 2010. A pH of 4 can only be reached by very high carbondioxide levels. The dynamics of the signals indicate eruptions and sediment movements from October 2009 till the end of the deployment.