PS93.1 Weekly Report No. 2 | 6 till12 July 2015
About phytoplankton, moorings and mud
Monday 06 July. Our today’s activities are mainly related to the Hovercraft camp and Yngve & Audun. How should we procede?
A lot of discussions, phone calls, decisions are to be made etc. Finally we all agree that we will recover all the dangerous goods. Yngve and the hovercraft will continue the drift experiment, and Audun will go onboard Polarstern. That means for Yngve another four to five weeks on the ice floe until finally he will be picked up with all equipment by another icebreaker. Yngve is quite optimistic about the coming weeks and a successful final phase of the drift experiment. Let’s cross our fingers!
Tuesday 07 July. We continue with our normal station work with oceanographic, biological and geological sampling activities. Here and now, we focus on the biology. The biological program of this cruise is concentrating on the smallest organisms of the Arctic Ocean water column, the so-called phytoplankton. Plankton describes all organisms, animals and plants, which drift in the water column and cannot swim against currents. Among bacteria this includes unicellular algae, which form the basis of the marine food web. Phytoplankton produce energy by transforming light energy and carbon dioxide into organic carbon. One side product of this process is the oxygen, needed by humans. If there is a shift at this basis of the arctic marine food web, as climate change and global warming might have severe impact on this basis of the marine arctic food web and may thus change the diet of larger animals such as e.g. birds and whales. To study how diverse they are and how the small organisms of the water column respond to environmental conditions, Steffi Gäbler-Schwarz is taking samples with a handheld net. These samples are investigated microscopically in a cold-lab (Fig. 1) and separately transferred into vials, so that the different algae species can be investigated further, back in the AWI Bremerhaven. Up to now the biological program on board has been very successful with 15 handheld net stations and 4 Zodiak trips. The latter have been carried out to sample algae and also sediments incorporated in the sea ice directly at the ice edge (Fig. 2).
Wednesday (08 July) and Thursday (09 July) are dominated by an intense coring and sampling party of the geologists. Two kastenlot cores and four gravity cores are scheduled within a short period of time – a lot of work for crew and scientists involved in these games! The second kastenlot run brings a 8.2 m long core on deck – the record for this expedition! After opening the kastenlot box and cleaning the sediment surface, an impressive sedimentary sequence is lying on the sampling table in the geo-lab (Fig. 3). Prominent color changes (red-brown-green-black), grain-size variations from clay to coarse sand, and alternations of laminated and homogenous, bioturbated intervals suggest major changes in the depositional environment during the youngest geological history. A great success, but also a lot of work for the geologists. In this situation we are more than happy that we have the ArcTrain Team onboard to help us handling all the mud. In comparison to the impressive kastenlot cores, our four small gravity cores are almost ignored. This is not „fair“! We should bear in mind that the locations of these short cores have been carefully selected to allow the reconstruction of the timing of the postglacial retreat of the Greenland Ice Sheet, a topic of ongoing and controversial scientific debate.
Large and small scale devices
Friday (10 July) is the day of our oceanographers. We are steaming towards east, the central Fram Strait. Our mission for today is to recover, respectively deploy three mooring systems. A more detailed outline by Wilken is added about these activities in the following section.
Saturday (11 July). We are on the way back towards the west, towards the ice edge. During this transit we shortly stop for one gravity corer run on Hovgaard Ridge, a location where we failed last year. This time we are successful and recover a short but good core. At 03:00 pm we again reach the ice, some sun shine occurs – just in time for our barbeque. While we are enjoying the nice scenery, meals, and drinks, we are steaming towards NW, towards the east Greenland shelf where we will have a major station on Sunday afternoon.
Sunday (12 July). We are still on the way to our next station. Progress is slow due to thick pack ice. In the afternoon, we are still 15 nm SE of the proposed coring location. However, the Parasound profile looks fine, several meters of young (Holocene) sediments are overlying older (glacial) deposits. Instead of continuing further to the NW and losing more time, we decide to have our station here. A perfect decision. Two long sections with several meters of Holocene sediments are recovered that will allow a detailed study of short- und long-term climate-variability during the last about 10000 years before Present. With this successful coring event we finish our research program in the western ice-covered East Greenland shelf area and steam towards the SE, about 120 nm through the partly heavy ice (Fig. 7).
Two more working days are waiting for us. Four to five more stations before we return to Tromsö.
That’s it for today. Kind regards to all our friends and families at home,
In the name of all cruise participants,
Ruediger Stein (12 July 2015)
(with a contribution by Steffi Gäbler-Schwarz to the biology program and a detailed report by Wilken von Appen about the oceanography day)