At the beginning of this week the weather in the Fram Strait was dominated by a stable high pressure system. These weather conditions characterized by low wind speeds and moderate temperatures facilitated our mooring work at 79°N. Especially the top floats of the mooring weighing 300 kg but also other heavy mooring equipment is way easier to handle at low sea states when the ship is not rolling. Our timing for this work couldn’t have been better!

Starting at the westerly end of our Fram Strait mooring transect we recovered six oceanographic moorings which were deployed in water depths between 2600 m and 200 m. As already described in the former weekly report, these moorings have been established to measure the exchange of water masses between the central Arctic basin and the Greenland Sea through the Fram Strait. All six oceanographic moorings were successfully deployed again. Furthermore a seventh mooring was deployed which is equipped with an autonomous underwater recorder. One of these instruments has already been deployed last week in the central Greenland Sea. These devices will continuously record the underwater soundscape for one year and the acoustic data will be analyzed for vocalizations of marine mammals as well as ocean noise levels. The data will provide detailed information on the seasonal presence of various marine mammal species in these areas and also provide baseline information on ocean noise levels of the Arctic environment. If the sea ice in the Arctic Ocean will further decline at current rates, shipping and so ocean noise levels will increase significantly in near future. For this reason it is very important to start immediately with these measurements in this fast changing environment to be able to monitor the increase in ocean noise levels and to evaluate possible effects on marine mammals.

The visual observers were very happy about the good weather conditions during the last days and sighted a significant number of marine mammals as well as birds in a lead of the Gulf Stream close to Spitsbergen.

The deployment of an autonomous seaglider was another highlight of the cruise. The sea glider changes its weight in the ocean from positive to negative bouyancy in order to perform upward and downward movements to depths of 1000 m. Each time it surfaces, it’s pathway is controlled from Bremerhaven via satellite connection.

Because of the fact that we finished our mooring work earlier than expected we were able to conduct a comprehensive CTD transect through the entire Fram Strait. In the course of this CTD transect we encountered heavy sea ice conditions accompanied by fog in the westerly part of the Fram Strait. Also the new infrared camera system is not able – because of physical limitations – to cope with these environmental conditions and to detect marine mammals in the vicinity of the ship. R/V Polarstern has recently been equipped with a new radar system which of course allows the officers to navigate the ship safely although the visibility is literally zero.

As always, there had to be enough time reserved to clean up the labs, to pack the scientific equipment, and to backup the collected data. Unexpectedly after we arrived at our last station the weather finally cleared up and the pristine sea ice twinkled in the sunshine. A very curious polar bear on a close by ice floe procreated a wave of enthusiasm onboard and almost all camera storage cards were filled in minutes.

We finished our successful cruise with these amazing impressions and a remarkable amount of collected data. We arrive in Longyearben, Spitsbergen Friday morning and will hopefully have a safe trip back home.

With best wishes from all onboard!

Gereon Budéus, Chief Scientist ARK XXIV-1
July 10th 2009