26 June 2008

Exactly on the day of the summer solstice, i.e. last Friday, we were able to finish the geodetic work on Greenland shortly after the sun had passed our northern meridian. Despite the - due to the relatively early time of the expedition – still dense pack and landfast ice we managed to transport the complete set of instruments by helicopter to Greenland and to install it there. This success was owed much to the favourite weather conditions, which have to be denominated as dazzling in every sense of the expression. Our stopovers in the ice were bearing the names: Jackson Isle, Shannon, and Store Koldewey. From the latter we had to cover so long distances that we were particularly grateful to possess an on board meteorological station with a staff of two. Reliable local weather forecasts are provided by them.

The midnight sun is bright, but not quite as strong as during noon. This resulted in upcoming fog, which made our way through the ice laborious. Naturally, with good sight, everything seems easy: From Polarstern’s bridge the assessment of the ice conditions is fine, satellite images are informative, and it is also possible to perform a helicopter survey to explore the best track for the ship. With bad weather, all three options cease to exist and the radar – not build for this purpose originally – reveals the sparse though best information. The fog accompanied us stubbornly the following days, but in the final end the ice edge was approached.

After we had to leave the ice-covered region last Sunday to the regret of most, we concentrated on mooring work during the remaining part of the week. Four moorings had to be recovered and the same number had to be deployed. Three of them carry autonomously profiling instruments, which measure the physical properties of the water between 100 m depth and the ocean bottom at 3700 m. The forth also carries an autonomous profiling instrument, but works in a reversed fashion: Installed in a water depth of 160 m, an underwater winch pays out rope in order to enable the ascent of the buoyant instrument to the water surface proper. This is a very innovative technique. (Usual moorings cannot contain instruments close to the sea surface because of the rough conditions there.)

A certain difficulty was posed by the fact that the latter system could not be exchanged but had to be redeployed using the same instrument as the year before. After recovery, data had to be extracted immediately, the condition of the instruments had to be checked, energy supplies had to be renewed and the instruments had to be resealed. Clearly, this takes a day or two, and the mooring cannot be redeployed immediately after recovery, as is usual otherwise.

Mooring work has been finished this morning. Now we continue our way eastwards with CTD-stations and collect water for the biologists and chemists.

Everyone on board is well and sends best wishes again, as do I.

Gereon Budéus, Chief scientist ARK XXIII/1