Monday (01 Oct 18).The final research week starts. For today as well as tomorrow a full coring program for the geologists has been scheduled. At two potential locations selected for drilling within the IODP program multicorer, giant box corer, gravity corer and kastenlot corer are used successfully to sample the near-surface sediments.
Despite this success, however, a wistful feeling remains. Originally our “Polarstern” Expedition has been planned to be carried out as part of the IODP drilling campaign. Finally the already scheduled IODP campaign has been cancelled as the additional money for hiring a Russian powerful icebreaker needed to break the ice under worst conditions, has not been available. This year, however, we did not find any ice at all the potential drill sites (Fig. 1), i.e., the drilling campaign could have been carried out without any additional icebreaker support. What a pity that we did not have known this in advance …..! Let’s hope and cross our fingers that the IODP drilling compaigh will become reality before the end of the running IODP phase.
Wednesday (03 Oct 18). We wake up in the morning, pancake ice around us. Meanwhile we have steamed back to “our” seamount in the central Amundsen Basin. As you may remember from one of the earlier weekly reports we have – based on the new seismic data - postulated a magmatic source of this structure. To get a further proof of this hypothesis we would like to use the rock dredge to sample the seafloor. If the sampled rocks would be mainly composed of magmatic rocks we have another evidence for our hypothesis. At 07:05, the dredge goes to water, under the command of our technician Norbert Lensch. A water depth between 3500 and 4000 m – a long way to go! One hour down to the seafloor, one hour sampling at the seafloor, and one hour back to the ship. At 10:30 the dredge is on deck, a sack full with mud and stones (Fig, 2). After a “funny” cleaning action at the aft deck, a large collection of small and big stones is on the table in the wet lab (Fig. 2) – but no magmatic rocks, no basalt! A second dredge run in the afternoon gives exactly the same results, partly strongly weathered sand-, silt- and claystones, partly covered by thick manganese crusts. Even we did not recover magmatic rocks, these dredges can be regarded as another highlight. The recovered stones belong more or less all to the same type of sedimentary rock suggesting an in-situ origin from the top of the seamount. Furthermore these rocks are certainly “old”, i.e., of pre-Quaternary age. If we can date these rocks, we also would get an idea about the minimum age of the (probably) underlying magmatic basement rocks. Maybe the sedimentary rocks represent time intervals when the Arctic Ocean was much warmer and ice-free – Pliocene, Miocene or even older? No limits for our “geo-fantasy” at the moment as we do not have real data to prove any of these ideas. These data, however, will be obtained by our future detailed investigations in the home labs
Thursday (04 Oct 18). The last geo-station, a gravity corer goes to water very early in the morning. That’s it, the end of the geology sampling and coring program. At 08:30 then the ultimate station of our expedition: a final drift buoy is deployed via mummy chair. This becomes a very short station. The buoy has just been put on the ice floe when a polar bear mom and her kid show up, coming very close to the ship and the buoy. Some movement or noise on the ship has scared the polar bears, and we continued our voyage towards the west. Thus, we do not know whether our two polar bears will come back to the buoy, play with the buoy ….. At 10:00, we stop all scientific research instruments and registration systems – this is the end of our research program!
The weekend, a special weekend (you will see later), is coming closer, introduced by pancake ice and thick fog, simply dull weather conditions! “Weather” is the key word – up to now another minor program dealing with meteorological measurements, has not been introduced so far. Dirk, this is now your chance – go ahead!
During our cruise in the Arctic waters, Dirk Olonscheck from the Max Planck Institute for Meteorology (MPI-M) performs atmospheric measurements in collaboration with Christian Rohleder and „Weather-Max“ from the German Weather Service (DWD). The main part of this work is the launching of radiosondes attached to a weather balloon. While the DWD launches one radiosonde per day at 12 a‘clock UTC, Dirk complements this base activity by launching three additional radiosondes per day every six hours (Fig. 3). This is part of the special observing period of the Year Of Polar Prediction (YOPP). Radiosoundings have a long tradition also in polar research. At the Third German Expedition to Antarctica in 1938/39, radiosondes were described the following: "The shining device is a tiny radio station, strong enough to be heard from a distance of 60 km. And due to a clever setup, this instrument of only about 1 kg of weight – including the battery – is constantly sending temperature, air pressure and relative humidity. Together with the wind data, the sum of the meteorological measurements provides everything that one can demand about the weather conditions. And this is from the sea level to more than 20 000 m height, i.e. far into the stratosphere." (*, translated from German)
Our radiosondes on board “Polarstern” only weight 100 g and the balloon is carrying them to a height of more than 35 000 m. However, for more than 80 years, the basic principle is the same! The collected data on the temperature, humidity and wind profiles of the atmosphere hopefully contributes to substantially improve the weather forecast here in the northern high latitudes, and are also used directly on board to judge the safety of our helicopter activities. As in earlier times, „the daily radiosounding belongs to breakfast, like brushing the teeth beforehand“ (*), but still many launches have plenty of visitors from both the scientists and the crew.
* Source: Ernst Herrmann (1941), "Deutsche Forscher im Südpolarmeer, Bericht von der Deutschen Antarktischen Expedition 1938-1939", Safari-Verlag Berlin
The especially curious ArcTrain students Amélie Desmarais and Samira Samini join the launches from early on. They get to know the procedure and were a valuable help for launching so many weather balloons in the last weeks. Many thanks to Amélie and Samira!
Thick low-level clouds and fog are characteristic for our cruise. Consequently, there has been rarely the chance for aerosol measurements that require an unobscured view on the solar disk to measure the direct solar radiation and to provide information on the number and size of air-pollution and salt particles in the Arctic air. However, the weather conditions have been excellent for another research activity on board the ship: the detection of the cloud base height using a cloud camera system that takes visible and thermal images of the ceiling every 10 seconds (Fig. 4). While we can get information on the cloud coverage and the height of the cloud top from satellite data, the cloud camera provides a view from below. Hence, we collect high-resolution data of the spatio-temporal variability of the cloud base height by measuring the brightness temperature of the clouds. This allows for an estimate of the warming of the underlying air mass. With engaged support from the ArcTrain students Amélie Desmarais and Aliaksandra Kazlova, we have already started to analyse the collected data on board.
We collected plenty of meteorological data during the expedition that will hopefully be an important contribution to a better understanding of the polar meteorology.
Many thanks, Dirk, for these insights into the weather business – but now back to our daily business, especially our weekend.
Saturday (06 Oct 18). 07:00 on the bridge, the captain changes the course to 290, we are steaming through ice-free waters towards WNW. At 09:41 we pass 83°05.1’ N, 56° 24.4’ E! Actually nothing special, or? If you remember what has happened on September 23, you would say “yes, an important step”!! On September we have documented (see 3rd Weekly Report) that with 83°05’ N we have reached the northernmost location of our entire expedition. This statement has to be withdrawn now! And we continue towards WNW: at noon we reach 83° 12.5’ N! Where does this end? – although most of the people have not realized the change of our course and certainly do not know why! Meanwhile small pancake ice floes are passing the ship, becoming closer and bigger (Fig. 5, upper left). Slowly the penny dropped!! We are approaching the ice edge, we reach the ice edge at 18:00 – exactly in time with the beginning of our barbecue. And this is now really the northernmost position of our expedition: 83° 38.7’ N, 44° 08.3’ E!! But this is not all – a few minutes later two polar bears on an ice floe (mom and kid, maybe the same we have seen three days ago?), followed by a – for Arctic conditions – already quite big iceberg, drifted along on starboard side. This is really a perfect staging by our captain that would fit into any movie. Congratulations and thanks a lot!! This makes our expedition to an unforgettable adventure to all the participants, especially the tyros. We have now some hours to enjoy this scenery and the farewell barbecue & dancing party, and say “good-bye” to the Arctic.
There is one person in our group, however, for whom this expedition is and remains unique and unforgettable - Ovie Benson, Bremen student from Nigeria. Today it’s Ovie’s 30. birthday that we all can celebrate together in front of this unique Arctic scenery. According to a Bremen unwritten law, the 30. birthday and being not married also ask for a “special treatment” (see the German “Wochenbericht”).
Sunday (07 October 18). At the end of the weekend another highlight has been scheduled for Sunday evening. Captain and Fahrtleiter invite for a cinema evening into the “Geräteraum”. The German cult movie “Die Feuerzangenbowle“ with Heinz Rühmann as main actor is shown, and the real “Feuerzangenbowle” (= glogg with some rum) can be enjoyed while watching the movie.
One final week, and we are back home!!
Best wishes from all of us,
Ruediger Stein
07 October 2018
(with a contribution by Dirk Olonscheck/MPI Hamburg on “Meteorology“)
