ANT XXV/5, Weekly Report No. 6
Punta Arenas – Las Palmas – Bremerhaven
Week 21: 18 May - 24 May 2009
Time is running so fast on board and the end of the expedition is coming closer and closer. “Polarstern” continued her cruise along the Spain and Portuguese coast at fine weather and calm sea conditions. The cruise was interrupted by CTD and RAMSES sonde stations. New sensors were successfully tested during a deep range CTD station on 18.05.09. The sky was mostly cloudy during the first few days of the week. This partly disturbed the irradiance measurements on board and on the Zodiac. The last station works for this cruise were done on the 20th of May 2009 at 17:00 local time. Station activities were completed and the scientists started to repack their equipment.
The Gulf of Biscay offered us his best weather and sea state. The sea was unexpectedly calm and we enjoyed on board the little rolling and pitching ship. The fascinating light and colours produced by the sun on the water animated the cruise participants to go out and to enjoy the beauty of nature. During the last days of the cruise, the weather improved and sunshine accompanied us all the time. We continued the evening lecture programme by talks on the meteorological and chemical works on board and the construction of the new German Antarctic station Neumayer III. The last two days were also used for cleaning laboratories, reporting and packing. This part of the cruise from Las Palmas to Bremerhaven was used for training a new generation of operators on the sediment echo sounder “Parasound”. This group reports:
The Parasound Group - from left standing: Jens Matthiesen, Gerd Kuhn, Julia Gottschalk, Frank Niessen, Ann-Kathrin Rohardt, Lars Max; from left sitting: Tanja Dufek, Jan-Rainer Riethdorf, Beate Slaby, Sze-Ling Ho
Report on Parasound training by Jan-Rainer Riethdorf (IFM-GEOMAR, Kiel), for all Parasound Team
"Supervised by Gerhard Kuhn, Jens Matthiessen and Frank Niessen (AWI, Bremerhaven) a Parasound training course is held this week on “Polarstern”. Seven PhD or undergraduate students from different research institutes or universities are participating in this course: Tanja Dufek (HafenCity University Hamburg), Julia Gottschalk (University of Bremen), Sze Ling Ho and Lars Max (AWI, Bremerhaven), Jan-Rainer Riethdorf (IFM-GEOMAR, Kiel), Ann-Kathrin Rohardt (University of Technologies, Dresden) and Beate Slaby (Ludwig-Maximilian-University/University of Technologies, Munich).
During the transit from Las Palmas back to Bremerhaven participants in the course will be trained for independent operation of the new hull-mount Parasound System P-70. The Parasound is an echo sounding system, especially for marine sediments, used to visualize the structure of the seafloor. This is possible by sending ultrasonic waves through the water column to the seafloor and by subsequent reception of their echoes. The waves are generated and received by a transducer/receiver plate which is mounted on the bottom hull of the ship. They can penetrate up to 200 m into marine sediments. Reflections contain information about sediment type and structure. In marine geology this is important to find out about the thickness of a sedimentary package in case coring is planned to be conducted.
This last part of “Polarstern's” cruise is particularly suitable for Parasound training, because the planned transit track back to Bremerhaven covers different geological structures, like deep sea basins, seamounts, the European continental slope and the continental shelf, which are covered either by soft sediments or hard rocks producing various kinds of echoes. Thus, the range of seafloor topography, water depth and sediment penetration allows to use all possible modes of operation under expedition conditions. Additionally to data acquisition the course will deal with data processing, data management and visualization as well as trouble shooting regarding both hardware and software problems.
Therefore, for us Parasound-operators, this training is an optimal preparation for the forthcoming expeditions of the research vessels “Polarstern”, “Maria S. Merian” and “Sonne” within the next two years.”
The DOAS-System on board "Polarstern": Jens Tschritter (l), Johannes Lampel (r)
The report on the DOAS System on Board „Polarstern“ is provided by Jens Tschritter and Johannes Lampel, Universität Heidelberg:
“Reactive halogen species play an important role in the photo chemistry of ozone and influence the oxidation capabilities of the troposphere. For example within the catalytic ozone destruction by BrO, the so called ‘detergent of the atmosphere’ OH-, is being produced. IO seems also to be crucial for condensation processes in the lower atmosphere.
Sources for reactive halogen species are inorganic compounds which react with sea salt aerosols, in polar regions also freezing seawater emitting Cl and Br directly on the extensive surfaces of frost flowers. In tropical regions emissions of halogenized organic compounds produced by algae are a more important source. The emitted compounds are later disintegrated by photolysis during daytime. This is e.g. to be observed near to upwelling areas on the west coast of Africa.
Total marine emission figures for halogen species are so far unknown.
Our measurements are based on the MAX-DOAS principle for which we record scattered light spectra for different elevation angles. By this way it is possible to obtain height profiles of the mixing ratios for different species. Measurements on the “Polarstern” have the advantage of covering large distances, tropical as well as polar regions. Often experiments occur onboard related to our measurements. Furthermore there have not been long term observations of open sea conditions for those species yet. Finally they are used for validation of satellite data.”
The “Polarstern” cruise ANT-XXV/5 was successfully completed on 24th May 2009, 04:00 h in Bremerhaven. Chief scientists Walter Zenk and Saad El Naggar would like to thank captain Pahl and his crew on behalf all participants for the fruitful and very effective assistance to us during this cruise. Also we would like to say goodbye to our readers and you will get the new reports for the next expedition soon.
Warm greetings to everybody at home,
Saad El Naggar
54°N, 08°E, 24 May 2009