ARK-XXVI/3, Weekly Report No. 8
Two crew members return from a two hour rubber boat maneuver for catching the mooring with a rope. (Photo: M. Hoppmann)
An instrument being rinsed after recovery. It harbors four years data of vertical temperature, salinity and velocity profiles. (Photo: I. Waddington)
26 September - 2 October 2011
Our expedition comes to an end. At the beginning of last week, we had a feeling of déjà-vu when recovering two more moorings which, as was the case with other moorings recovered many weeks ago at the beginning of the cruise, had malfunctioning releasers and did not surface. Once more a boat maneuver for capturing the moorings with a rope was our only chance and once more it was a full success. I daresay that no other ship and no other crew would have been able to save these moorings – which have been attached to the seafloor in this harsh and remote region for four years. A first glance at the data revealed that some instruments, although designed to collect data for one or two years, have been operating over the entire time and provide time series of four years. Thus the recovery saved a unique treasure of long-term observations in the central Arctic Ocean.
Exciting measurements were obtained at the finish in the Laptev Sea where we observed the impressive contrasts in temperature and salinity at the confluence of two current branches. Both branches originate from the same current in the North Atlantic but when entering the Arctic one branch flows through Fram Strait thereby mostly keeping its high temperature and salinity and the other flows through the shallow Barents Sea where it is getting colder and less saline through mixing with continental runoff. With the large-scale survey of our cruise we found that after the confluence the branches separate once more and spread throughout the entire Arctic Ocean, but contrary to what was assumed before, follow different circulation pathways before they join again in Fram Strait.
Finally we turned homewards – brightened up by a few clear nights with northern lights. It´s autumn here, which explains the succession of North Atlantic low pressure systems crossing our way irrespective of our efforts to avoid them. We are looking forward to being back in Bremerhaven soon!
Before concluding I want to thank Russ Hopcroft and Nicolas Cassar for helping with the English version of the reports.
For the last time best wishes from Polarstern,
Ursula Schauer
Salinity profiles 20 km apart at the confluence of saline Atlantic water approaching from Fram Strait and low Atlantic water that flows through the Barents Sea and has been freshened there. (Graphics: B. Rudels)
Polar lights over Polarstern. (Photo: M. Hoppmann)
