Spitsbergenbanken from the deep south to the shallow north
Cruise diary: On the last Mareano cruise of the year to Spitsebergenbanken, we had strong winds and 4-5 m high waves south of Hopen. With the video rig parked on the seafloor at 150 m depth, we could observe how suspended sediments and animals living on the seafloor drifted back and forth in the same wave motion as the research vessel G.O. Sars. This shows that waves, in which we commonly think only occur on the sea surface, may also affect the seafloor at large depths.
Author: Valérie Bellec, Reidulv Bøe, Aivo Lepland and Ingrid Leirvik Olsen, Geological Survey of Norway, and Børge Holte, Institute of Marine Research
The cruise started in the 250-350 m deep area called Kirkegården (The Graveyard). The bottom currents in the area are weak, allowing very fine sediments to settle out of the water column and drape the seafloor. However, the layer of fine-grained sediments is thin, often only a few centimeters thick. Beneath we either find bedrock or more coarse-grained sediments (moraine) covering the bedrock.
The bottom currents become stronger as we move upslope towards Spitsbergenbanken, resulting in coarser sediments with abundant gravel and cobbles. In areas shallower than 150 m we clearly observe the effect of waves on both the bottom water and seafloor. Caused by strong wind and 4-5 m waves, the animals and suspended particles on the seafloor move back and forth in phase with the waves felt onboard the research vessel G.O. Sars. Because of wave activity and strong bottom currents the finest sediments are not deposited, resulting in a seafloor largely covered by gravel and cobbles.
Towards the top of the bank we find a rich fauna, indicating that the animals enjoy the high energy environment with a rocky bottom and strong currents. The seafloor is covered by a high quantity of calcareous fragments including both living and dead shells, barnacles and other organisms.