Die 350. Forschungsfahrt des FS POSEIDON fand vom 26. April bis 10. Mai 2007 unter der Fahrtleitung von Dr. Gerd Krahmann stat

Krahmann, Gerd

English

OceanRep

„ Sunday 22nd to Tuesday 24th of April everybody arrived in Funchal on Madeira. Our container with the seismic equipment was loaded onto Poseidon on the 24th and we unpacked and stowed everything on the 25th. At 9am on the 26th we left port to steam northeast towards the working area south of Portugal in the Gulf of Cadiz. Wind force 5 to 6 right out of port gave a proper introduction to the two of us who had never been on a cruise. After a bad day and some pills they are feeling fine now like the rest of us.  After leaving the exclusive economical zone around Madeira we did a test CTD and XBT station in the afternoon of the 27th. All instruments worked well and we already found thermohaline structures which should be reflective to seismic sound.  Today on the 28th we finally reached the work area to start with the deployment of two  autonomous glider systems. Unfortunately a late test with one of them resulted in a failure  we had already seen on a previous cruise. Since this failure is rather serious (it lost  all communication and it was only after power cycling able to reconnect) it is not going to get wet. Three hours ago we deployed the second glider and after initial tests are now  doing the first serious dive. We hope that a small warning this instrument...  That's how far I came with this report.  Here's the rest.  The small warning turned out to be more serious. The glider has problems with its fin.  Though the steering worked most of the time, it complained that the  speed with which the  fin turned was too low. We recovered the second glider shortly after.  I do, however, have hope that this problem can be overcome so that it can be redeployed.  At the moment we are doing a CTD/XBT transsect towards the location of two ocean  bottom hydrophones (OBH) which we intend to recover tomorrow. Later that day we hope to be joined by RRS Discovery and begin the seismic oceanography experiment in ernest.   Despite these setbacks the mood is still good and everybody on board enjoys the good food and the hospitality of Poseidon's crew. “ 

1. Wochenbericht POS350

 „This third weekly report is coming early as we have left the  experiment area and are now steaming on a dead calm sea under blue  skys towards Lisbon ...  This morning we ended station work with a second 12 hour long  vertical seismic profiler (VSP) with 10 hydrophones attached to the  heavy load winch cable. RRS Discovery therewhile steamed in a star  shaped pattern around us continuously shooting her air gun arrays...  Since the last weekly report we had continued towards the southern  connecting corner of  the two intended sections. From the corner we continued another 25  miles crossing the location of a recent earthquake. Over these 25  miles we deployed 7 OBH systems while RRS Discovery finished  the  section and turned around to pass over the OBH. After that we rushed  to quickly recover the OBH and catch up with RRS Discovery. Some 10  hours later we met her again as they had turned aroun to pass again  over a particularly interesting hydrographic feature they had  discovered in the seismic data. A rather strong horizontal boundary  was visible between relatively pure Mediterranean Overflow Water  (MOW), possibly a meander of the boundary current, and the  surrounding background of diluted MOW. We decided to delay the  original plan of the second section towards Cape St.Vincent and do a  more detailed study of the region. While FS Poseidon took center in  the MOW with a 12 hour long Yoyo CTD RRS Discovery looped twice  around us overall crossing 5 times between the areas of the two  waterbodies. Thereafter we continued on the interrupted section to  stop safely outside of the Traffic Separation Scheme at the Cape.  Crossing it towing a 2.4km streamer would just have been too  dangerous. We then turned westsouthwest to again find the border of  the two watermasses. Another turn to the eastsoutheast brought us  back to the location of the Yoyo CTD. There we did the second VSP  over strong MOW with a very sound-reflective layer embedded intrusion  of diluted MOW. Before we began this station we used the last chance  and the continuously improving weather to get the two ships close  together and lower a zodiac. After exchanging some small gifts ... we  took a good memory card-load of pictures and some video footage.  Tomorrow most of us will fly back home after a mostly successful  cruise on FS Poseidon.“ 

3. Wochenbericht POS350

„Last week ended with the recovery of a malfunctioning glider. We  then turned northeast and began work on a CTD/XBT/LADCP transsect. On  Sunday 29th of April we recovered 2 OBH systems that were deployed by  RRS Discovery some 10 days earlier. We then turned around to a  location at which RRS Discovery had done repeated seismic data  collections. A few hours later we started deploying our Vertical  Seismic Profiler (VSP), 19 self-recording hydrophones lowered from  the ship.  FS Poseidon's captain and mates bested themselves when, for the next  18 hours, they were able to keep the ship steady within a cable of  the nominal position. RRS Discovery must have believed that we had an  automated positioning system. After recovering the VSP we did a 13  hour CTD-Yoyo station while RRS Discovery deployed their seismic  streamer system. After she had passed FS Poseidon we together began a  seismic/CTD/XBT/LADCP transsect towards the northeast. Following the  constantly moving RRS Discovery we approached the end of their  streamer, did a CTD station, and afterwards hurried to catch up  again. Doing this we were and are able to keep a station distance of  about 12nm.  An XBT was thrown between each CTD to increase resolution. At the end  of the transsect a star shaped pattern of seismic data collections  was planned that we intended to complement with CTDs, XBTs,  Microstructure profiles, and OBHs. When we arrived there on the 2nd  of May the weather had, however, degraded to Beaufort 7-8 and RRS  Discovery took in their streamer. For the next 24 hours we took some  shelter near Faro. On the 3rd we finally did the star shape. All this  within miles of the extremely busy shipping lane between Gibraltar  and Cape St.Vincent.  After the star we returned to the transsect this time in  southwesterly direction.  Now we are nearing its end and hope to again attempt a glider  deployment. The conditions are, however, not favourable at the moment  with winds 6 to 7 and rough seas. Five hours later: Indeed the  conditions did not allow the deployment of the glider. A whale next  to the ship and pigeon on deck today, a group of Dolphins surfing our  bow wave near Faro, and terns at night were welcome distractions from  the work around the clock. “ 

2. Wochenbericht POS350

Abstract

Similar works

Full text

Available Versions

OceanRep

OceanRep

OceanRep