North-East Greenland

RV 'POLARSTERN' ARK-XXIV/3
Reykjavik – Bremerhaven
31 August to 6 September 2009

This time our transit through the ice towards the North-East Greenland coast was without major delays. Sunday morning we recovered three earthquake-recording stations in total, which had been drifting for almost 10 days on a large ice floe in the Fram Strait.

After four hours the helicopters and instruments were back on the ship, and we proceeded to sail towards the Djimphna Fjord. The weather forecast was perfect. Blue sky and warm temperatures brought most of us on deck to observe how the ship entered the fjord. RV Polarstern is most likely the first vessel to ever sail through these waters. Therefore, all precautions were taken to carefully chart the water depths. During the entire day, the two helicopters were extremely busy picking up the geology camp and the GPS recording stations. In the late afternoon, both helicopters were back on the vessel, and the ship left the Djimphna Fjord heading eastwards.

On September 4th, we arrived in the Boreas Basin again, and immediately started to recover the ocean bottom instruments. For almost 10 days the instruments recorded small and very large earthquakes around the globe. The general setup is that a metal frame acted as anchor, keeping the instruments on the seafloor. To recover the instruments, we sent an acoustic release command from aboard the ship. Then, the anchor was disconnected from the main instrument which then started to rise to the sea surface. The instrument itself consists of a seismometer, a recording unit and a battery pack. From its own buoyancy it rises with a speed of 1.2 m/s to the surface.

Here, a transmitter and an additional flashlight during night time were automatically switched on to allow an easy sighting and fast recovery of the instrument. Finally, two crew members approached the ocean bottom instrument with a rubber boat and brought it back to the vessel. On deck, the digital data were immediately downloaded, and stored on one of the ship’s computers. This task will keep us busy until next Tuesday.

During this eventful week, we definitely benefited from good weather conditions. Except for a few foggy days, we had good visibility for the helicopter activities and calm sea. However, even a good progress of our experiments at the end of the week could not compensate the days we lost by passing the large and partly dense ice fields on the shelf.

Best wishes to the readers at home

Wilfried Jokat
September, 6th, 2009, North-East Greenland
78°55’N  006°56’E        +6°C