The last recovery of the ROBIO
The acoustic lander left behind to do long time logging
Date:29 July, 2004
Author: Odd Aksel Bergstad and Thomas de Lange Wenneck (IMR, Norway)
This was a day of relatively few highlights. Starting last night, a strong gale was blowing through the morning and by the afternoon there was no improvement. We were at our last station, did our CTD and deployed the ROBIO lander, but other activities were impossible. We might have managed to trawl despite of the relatively heavy swell, but yesterday’s two failed trawls showed that a threatening technical problem with the trawl winches had now become severe. Little or nothing could be fixed at sea, so we had to abandon trawling. Luckily, we had by then completed 21 tows without any major technical faults.
It is dangerous to put out and retrieve an ROV in heavy swell. The vehicle is lifted over the side by a crane and basically dropped into the sea, and during that operation it may hit the ship’s side and get damaged. Also, the umbilical cable can be damaged and even break if the tension becomes too irregular or abrupt.
We really wanted to finish in style by doing a couple of good ROV dives at the end of the cruise, but the weather just would not co-operate. The PI, after careful and repeated inspection of weather charts, finally had to accept that there was no other solution than to announce that all sampling activities had to stop. At that time we had about 20 hours left of our scheduled cruise time.
The ship started steaming for Aberdeen, Scotland, at 18:30 Hrs (Norwegian time). The scientific work of Leg 2, and indeed the entire MAR-ECO expedition 2004, is over. Those of us who have played active roles in the planning of this effort for a long period of time now experience these strange contradictory feelings of relief that the job is done and reluctance to accept that it is now over. We have learned a lot, but still so little.
We are leaving one thing behind. A Bergen Acoustic Lander will keep recording and logging acoustic scatterers passing by above it for about a year from now. It is placed on a hill in the middle MAR-ECO box. If it functions and the batteries last, we will learn more about the seasonal dynamics of scattering layers in this fascinating area. On one condition, however! Somebody has to pass by the site and pick up the lander for us.