Blog from RV Lance: Under-ice turbulence instruments recovered

Today we recovered our under-ice turbulence instruments after two days of operation. The system consists of eight different sensors fixed to an eight meter long aluminium pole. The instruments are deployed through a large hole drilled through the sea ice, and connected to a support frame, a power supply system and laptops at the surface. We have spent a lot of time designing, building and testing the system and it felt great to see that it had all been working continuously for two days in low temperatures.

Lisbeth Håvik (Univ. of Bergen) and Arild Sundfjord (NPI) deploying the turbulence instrument mast through hole in sea ice.

Lisbeth Håvik (University of Bergen) and Arild Sundfjord (NPI) deploying the turbulence instrument mast through hole in sea ice. Photo: Tor Ivan Karlsen / Norwegian Polar Institute

First half of the instrument mast below the ice.

First half of the instrument mast below the ice. Photo: Peter Leopold

Harvey Goodwin, Lisbeth Håvik  and Arild Sundfjord recovering the turbulence instrument mast after two days of measurements. RV Lance in the background.

Harvey Goodwin (NPI), Lisbeth Håvik  and Arild Sundfjord recovering the turbulence instrument mast after two days of measurements. RV Lance in the background. Photo: Angelika H. H. Renner / Norwegian Polar Institute

The instruments measure variations in temperature, salinity and water motion just under the sea ice, and from this we can calculate how much heat is released from the underlying warm Atlantic Water and up to the sea ice, and how much salt is rejected from the ice when it freezes. Using these data together with various supporting measurements made from the ship, such as wind speed, air temperature and water currents at different depths, our aim is to understand how the turbulent mixing is generated and how much heat can be brought up to melt the ice. This knowledge is essential to produce better models of sea ice behaviour.

It was the first time we used our new under-ice system throughout a full ice drift station and we were very happy to see that it collected data the whole time. The hole it had been deployed through two days before was refrozen when we came back to retrieve it, but it was fairly easy to get through the surface using a regular axe, without damaging cables and the mast. Good thing the whole thickness of 130 cm was not refrozen!