PS115.1 – weekly report Nr. 3 | 20.08. – 26.08.2018
Surprising ice conditions favor measurements further north
[27. August 2018]
The second half of our cruise started with a northwesterly directed transit. To follow the originally planned seismic profiles we would have had to cross an ice field of approximately 40 nautical miles.
This would have posed as a great threat for our dragged streamer and airguns, leading us to the decision of aborting the original profile plans for ones further north in hope of better ice conditions.
Larger ice-free areas north of 83°N are highly unusual, hence science program at that latitude was not considered in the planning prior to the cruise. Anyhow, satellite data showed a 50-100 kilometers large ice-free surface (seasonal polynya) of the northeastern coast of Greenland caused by katabatic winds that originate from the Greenlandic ice cap and push away coastal ice.
Seeing this as a spectacular opportunity to survey unmeasured areas up to more than 84°N in the Lincoln Sea, we restarted seismic profiling with the 3 kilometer streamer after leaving the mentioned ice field behind at 83°N on Sunday morning.
Of special interest for us was the Morris Jesup Rise, a sub-seabed structure that corresponds with the 500 kilometer distanced Yermak Plateu on the other side of the Gakkel ridge. Their possibly continental origin as also the process of their movement during the opening of the Arctic Ocean to their present position is subject of great discussion and essential for the reconstruction of regional geological developments.
At 84°18.73’N we reached the end of the BGR’s most northerly reflection seismic profile so far. Thickening ice made us shift our work westwards to the eastern Lincoln Sea, where helicopter borne ice reconnaissance promised better working conditions.
After finishing four more seismic profiles in the eastern Lincoln Sea on Tuesday, reflection seismic was paused and all outboard devices were retrieved until midnight the following day.
In addition to the reflection seismic data, that depicts the shallower crust, a refraction seismic profile was collected, consisting of 9 equally spaced (10 km) ocean bottom seismometers (OBS) for further insight to deeper crustal structures such as the boundary of Greenland and the Morris Jessup Rise.
We terminated the profile Wednesday evening and began the, because of the ice, challenging retrieval of the OBSs. In this we were fully successful thanks to the perfect preparation and programming of the OBS and essentially the experience of the deck’s crew and the nautical officers, our special regards go to captain Wunderlich and his crew.
Without a break the program switched directly to geological sampling, including gravity corers and box corers to analyse local marine sediment before RV Polarstern headed west to a position approximately 40 nm away at which dredging of rock of the Morris Jesup Rise was scheduled.
Satellite pictures had already implied that driving through ice would be necessary to reach our destination. Yet strengthening northerly winds changed the ice conditions so significantly and rapidly that an estimation of transit time grew increasingly unpredictable, thus we had to drop the dredging location (approximately 15 nm away from the location) to not risk a delay of our arrival in Longyearbyen.
As an alternative we changed our course to the mainly ice-free Wandel Sea at the northeastern tip of Greenland at which we arrived on Saturday after a 200 nm transit.
Surprisingly we had radio contact with the Canadian icebreaking bulk carrier Nunavik on its way toward the Lincoln Sea for reconnaissance surveying, from which one can derive that the additional pull back of Arctic ice probably sometimes opens the northern route around Greenland to Baffinbay resulting in an additional Arctic seaway in the future.
With the best of wishes from board
On behalf of all colleagues
Volkmar Damm
Position 80°52‘N, 03°25‘W
Contact
Science
Dr. Volkmar Damm
+49-(0)511-643-3226
Volkmar.Damm@bgr.de
Scientific Coordination
Rainer Knust
+49(471)4831-1709
Rainer Knust
Assistant
Sanne Bochert
+49(471)4831-1859
Sanne Bochert
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