LOMROG II 2009 2nd Field Report

Work with the seismic equipment mounted at the back of the ship

Work with the seismic equipment mounted at the back of the ship. Foto: Daniella Gredin.

Work has started

Received from Daniella Gredin, The Swedish Polar Research Secretariat

Edited by Henrik Højmark Thomsen, GEUS

12 August 2009

Icebreaker Oden

Position: 88°N 133°E

Weather: Thin clouds, temperature 0.3°C, wind 4 m/s

After eight days’ voyage, we arrived on Saturday 8 August at the first position where measurements were planned. Oden was gently placed in a small opening in the ice and drifted slowly with the ice during the measurements. When we had finished work about 10 hours later, we had moved 4–5 km to the south-west.

We made two profiles with the CTD instrument, which is measuring salinity and temperature of the seawater and can also be used to retrieve water samples. The CTD results are very important for later calculations of the precise water depths. The first measurement went down to a depth of 4362 m and lasted about three hours. Water was taken from depths of 4300, 350 and 50 m, and was subsequently filtered to capture bacteria. The filters were treated chemically and frozen for later DNA analysis. At the second location measurements were made down to a depth of about 300 m.

Ice conditions have varied much during the voyage. Sometimes it has been light ice conditions with many large openings, where it is easy to move for Oden. Other times Oden must struggle through more coherent thicker ice cover. Out on deck, you can hear a huge groan, when the ship slides up on the ice surface to break it. Along the hull, large blue pieces of ice shoot out of the water as corks. On the bridge it shakes violently when the ship is breaking ice, and you need a steady hand to avoid making mistakes when writing on the computer.

On Sunday 9 August, when we left the first working area, the geophysicists started the seismic measurements to map the geology under the seabed. From airguns, sound waves are sent down into the sea and the signals which are reflected from the geological layers beneath the seabed are then collected. The airguns and the hydrophones which are listening to the reflected signals are mounted on a long cable, which is dragged after the ship, when measurements take place.

Ice conditions were far from optimal for the seismic measurements, and it was a complicated and difficult operation. The geophysicists had problems with the cable, because of the ice moving around the hull of the ship. The seismic work went better later in the night, when there was more open water, and they have now collected about 40 km of data.

The CTD instrument ready for measurements.

The CTD instrument ready for measurements. Foto: Mike Lamplugh

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